1.
2 reasons why OI Tarda is less severe than OI Congenita: 1)It is NON-FATAL
2)TREATMET IS AVAILIBLE
2.
3 Major Disorders of Collagen Synthesis: 1)Scurvy
2)Osteogenesis Imperfecta
3)Ehlers-Danos Syndrome
3.
3 Major Modified AA's present in Collagen: -->All involve HYDROXYLATION RXN's:
1)3-hydroxyproline
2)4-hydroxyproline
3)5-hydroxylysine
-->Hydroxylation is an example of POSTTRANSLATIONAL MODIFICATION
-->Hydroxyproline is important in stabalizing the triple-helical structure of collagen b/c in =itmaximizes **INTERCHAIN HYDROGEN BOND FORMATION**
-->NOTE: Proline & Hydroxyproline combined contribute to ~ 30% of residues on collagen
4.
6 General Steps in the biosynthesis & assembly of collagen: 1)Synthesis (RER) --> Inside Fibroblast
2)Hydroxylation (ER) --> Inside Fibroblast
3)Glycosylation (ER) --> Inside Fibroblast
4)Exocytosis --> Inside Fibroblast
5)Proteolytic Processing --> Outside Fibroblast
6)Cross-Linking --> Outside Fibroblast
5.
Amino Acid sequence of a portion of the α1 chain of collagen: -->Are long stetches of (-Gly-Pro-Pro-HyPro-)
6.
Biological process btwn. Hydroxylation & Glycosylation Step in biosynthesis of collagen: -->**Addition of Asn-linked oligosaccarided to collagen**
7.
Biosynthesis of Hydroxyproline & Hydroxylysine: -->Requires **VITAMIN C(Absorbic Acid)* *Molecular O2*, and *IRON (Fe2+)**
-->Deficiency in Vitamin C lead to disorder in bone, teeth, gums, & skin:
1)Ex.1 ***Scurrvy
2)Ex.2***Decr. immune response
8.
Bisphosphonates: -->A pharmaceutical treatment for OI
-->MOA **INHIBITS OSTEOCLAST ACTION** which can lead to:
1)Incr. tensile strength
2)Incr. bone mass
-->2 major drugs can be taken:
1)Ibandronate (**BONIVA**) --> One tablet per month
2)Alendronate (**FOSAMAX**) --> One tablet per week
9.
Clinical Signs of Marfan Syndrome: 
-->The damage caused by Marfan syndrome can be MILD or SEVERE
-->Patients with Marfan syndrome are usually **TALL & THIN** with disproportionately long arms, legs, fingers, & toes
-->The abnormal microfibrills cause:
1)Weakened aortic wall
2)Reduced Structural integrity of the lens zonules, ligaments, lung airways,& spinal dura
3)Incr. susceptibility of fibrillin to PROTEOLYSIS
**Overall affect of abnormal microfibrils is PES EXCAVATUM, AORTIC ANEURYSMS (Dialated Aorta), HEART MURMURS, & INCR. RISK OF COLLAPSED LUNGS**
10.
Common Clinical Signs of OI: -->Common clinical signs:
1)**MUTIPLE FRACTURES WITH MINIMAL TRAUMA** (may occur during the birth process)
2)**BLUE SCLERA**(due to the translucency of the connective tissue over the the choroid)
3)Hearing Loss (due to abnormal middle ear bones)
4)Dental imperfections (due to lack of dentin)
5)"Humped-back" (kyphotic) (due to a rotated & twisted spine)
11.
Common locations where elastin can be found: 1)Large arteries (Ex. Aorta)
2)Lung Wall
3)Liagaments
12.
Comparison of Fibrous vs. Globular Proteins: 
(1) For Globular Proteins, think of **immunoglobins**in association with diff. characteristics
-Are immunoglobins compact? --> YES
-Are immunoglobins soluble in H2O? --> YES
-Do immunoglobins have a complex secondary structure? --> YES (combination of α-helix, β-sheet, & loop structures)
-Would a compact immunoglobin need to held by covalent forces in its quaternary structure? --> NO (Held together by non-covalent forces)
-Would an immunoglobin be part of a group of proteins that fxn. in all aspects of metabolism? -->YES
(2)For Fibrous Proteins, think of **hair/keratin** in association with diff. characteristics:
-->Is hair/keratin compact? --> NO (Extended)
-->Is hair/keratin soluble in H2O? NO (Insol. in H2O or lipid bilayer)
-->Does hari/keratin have a complex secondary structure? --> NO (Simple;Based on 1 type only)
-->Would a extended hair/keratin mol. need to held together by covalent forces in its quaternary structure? --> YES
-->Would hair/keratin be part of a group of proteins that fxn. in all aspects of metabolsim? --> NO (Only fxn.'s in structure of the body/cell)
13.
Desmosine Cross-Link: -->Formed from **4 Lysines** where:
1)3 of the lysines are OXIDIZED
2)1 of the lysines remain unaltered
-->Isodesmosine cross-links are responsible for the **YELLLOW COLOR OF ELASTIN**
14.
Difference in Hydrogen Bonding betwn a COLLAGEN TRIPLE HELIX & AN ALPHA-HELIX OF A PROTEIN: 1)For Collagen:
-->The hydrogen bonds form btwn. SEPARATE CHAINS ("Interchain")
2)For α-helix of a protein:
-->The hydrogen bonds form btwn. residues of the SAME CHAIN ("Intrachain")
15.
Effects of smoking on α1-AT methionine: -->***Smoking inactivates the methionine residue, which inhibits α1-AT from neutralizing the effects of ELASTASE or any other protease
-->Smokers have an **elevated rate** of lung destruction & a poorer survival rate than NON-SMOKERS
16.
Ehlers-Danlos Syndrome (EDS): 
-->Refers to a heterogeneous group of generalized CT tissue disorders that result from FAULTY COLLAGEN SYNTHESIS
-->Caused by a deficiency of collagen-processing enzymes (Ex. Lysyl Hydroxylase; Procollagen Pepidase) involved in the proteolytic processing and/or cross-linking of tropocollagen (***Step theat EDS Inhibits the biosynthesis of collagen)
-->While the disorder can affect multiple types of collagen, the clinically most important type of collagen affected is **COLLAGEN TYPE 3**
-->Most common clinical signs:
1)**Hyperextensible Skin* (b/c EDS patients also show defects in **Collagen TYPE 1)
2)Tendency to bleed (easy brusing)
3)Hypermobile Joint
17.
Elastase: -->A powerful PROTEASE that is released into the extracellular space
-->Has the ability to DEGRADE structural proteins in a variety of tissues, INCLUDING the ELASTIN OF ALVEOLAR WALLS
18.
Enzyme responsible for the hydroxylation of proline/lysine: **PROYL/LYSYL HYDROXLASE**
19.
Features of Collagen Fibers: -->Formed by **STAGGARED ARRAYS** of tropocollagens
-->Contain 40 nm gaps btwn. adj. tropocollagen (since tropocollagens are 300 nm long) known as HOLE REGIONS
20.
Features of collagen-related diseases: -->Commonly arise from EITHER (i) genetic defects, OR (ii) nutritional deficiences that affect any process involved in the normal collagen production
21.
Features of Hydroxylation Step of Biosynthesis of Collagen: -->Selected (**NOT ALL*) proline & lysine residues are HYDROXYLATED to form *hydroxyproline & hydroxylysine residues**
-->The hydroxlyating enzymes (proyl / lysyl hydroxylase) are required for these rxn's, which require:
1)Vitamin C
2)Fe2+
3)Molecular O2
22.
Features of Osteogenesis Imperfecta (OI)("Brittle Bone Disease"): 
-->Known as a heterogeneous group of inheritied disorders distinguished by bone that easily BEND & FRACTURE
-->Mechanism:
1)Bone resorption is GREATER than bone deposition b/c the OSTEOCLAST activity is ENHANCED
2)The incr. in osteoclast activity is believed to be due to the lack of nucleation sites due to the decr. formation of collagen
3)Treatment with **BISPHOSPHONATES** can correct this
-->2 Major Forms based on (i) age of onset & clinical severity:
1)Congenital -->Type II OI ("Osteogenesis Imperfecta Conginita")
2)Acquired --> Type I OI ("Osteogenesis Imperfecta Tarda")("Tarda" --> THINK TARDY IS LATE)
23.
Features of Scurvy: 
-->Caused by a vitamin C/absorbic acid deficiency, where **propyl & lysyl residues cannot be hydroxylated**
-->As a result, collagen fibers cannot cross-link (last step) which leads to :
1)Decreased tensile strength
2)Defective connective tissue
-->Patient will present with the following:
1)**Bruises on the limbs (due to subcutaneous extravasations of blood)(See image*)
2)Sore, spongy gums
3)Loose teeth
4)Fragile blood vessels
5)Swollen Joints
6)Anemia
24.
Features of Synthesis Step of Biosynthesis of Collagen: -->Genes from the pro-α1 & pro-α2 chains of polypeptide precursorsvare transcribed into mRNA's
-->mRNA is translated into collagen α chains known as the polypeptide "PREPRO-α COLLAGEN"
-->Preprocollagen is extruded from the ER to the lumen of the ER, where the signal sequence is REMOVED
1)Removal of the signal sequence causes the formation of "PRO-α COLLAGEN"
25.
Features of the Cross Linking Processing Step of the Biosynthesis of Collagen: -->Reinforcement of many staggared TROCOLLAGEN mol. by **covalent lysine-hydroxylysine**cross linkages create the formation of COLLAGN FIBRILS
-->Formation of the cross linkages are catalyzed by**LYSLY OXIDASE**
26.
Features of the Emphysema resulting from α1-AT deficiency: -->Usually caused by a genetic defect that codes for α1-AT, but the substitution of LYSINE FOR GLUTAMIC ACID (GAG --> AAG)is the most common mutation that causes the deficiency in 2-5% of emphysema patients in the U.S.
1)Homozygotes for the mutation are at risk for the development of emphysema
2)Heterozygotes contain adequate levels of α1-AT to protect the alveoli from damage
-->**Because α1-AT is syn. in the LIVER, the polymerization of the mutated protein in the ER of hepatocytes can cause **LIVER CIRRHOSIS** due to its accumulation in the liver
27.
Features of the Exocytosis Step of the Biosynthesis of Collagen: -->Exocytosis of procollagen into the EXTRACELLULAR SPACE
28.
Features of the Glycosylation Step of Biosynthesis of Collagen: -->Selected **HYDROXYLYSINE RESIDUES** are glycosylated with GLUCOSE & GALACTOSE
-->The formation of **PROCOLLAGEN** (A triple helix of 3 collagen α chains) occurs via the follwoing steps:
1)Assembly of 3 pro-α chains
2)INTERCHAIN disulfide bonds form
29.
Features of the Proteolytic Processing Step of the Biosynthesis of Collagen: -->The cleavage of the terminal region of procollagen by specific peptidases transforms **PROCOLLAGEN* into *TROPOCOLLAGEN**
30.
Features of the structure of elastin: (1)Is derived from the precursor polypeptide TROPOELASTIN
-->Tropoelastin is secreted into the extracellular space where it interacts with specific glycoprotein microfibrils (Ex. **FIBRILLIN**)
-->Either **DESMOSINE* or *LYSINONORLEUCINE** links 4 or 2 molecules of tropoelastin mol. together, respectively
(2)AA composition of elastin
-->About ~80% of the residues came from the 4 AA's:
a)Glycine (33%)
b)Alanine(23%)
c)Valine (13%)
d)Proline(10%)
(3)Secondary Structure of Elastin
-->**Lacks a regular secondary structure*
-->Contains a DIFFERENT type of helix structure from α-helix structure normally found in proteins
1)An unordered coiled structure
-->Is made from a helix of **REPEATING β-turns**, so it is referred to as a "β-Spiral"
31.
Features of Triple Helix of Collagen: 1)Contains 3 separated polypeptide chains arranged as a **LEFT-HANDED HELIX**
2)Contains 3.3 residues per turn
3)Each chain forms **hydrogen bonds** with the other 2 to promote STRENGTH
NOTE: The presence of **PROLINE* means that the helical formation is an *α-chain** [ NOT an α-helix]
32.
Features that contribute to the strength of collagen: 1)**Triple Helix SECONDARY Struc.**
2)Assembly of **tropocollagen** subunits into a fiber
3)Chemical **Cross-linking**
33.
Fibrillin & its role in the creation of elastin: -->A glycoprotein microfibril which serves a a scaffold onto which tropoelastin polypeptides are OXIDATIVELY DEANIMATED by lysyl oxidase
1) Such deanimation creates ALLYSYL SIDE CHAINS
-->The allysyl side chains are used with 1 unaltered lysyl side chain to form a DESMOSINE CROSS LINK
-->The desmosine cross-linked structure is the one that creates ELASTIN
34.
General Features of biosynthesis of Collagen: -->FIBROBLASTS (or OSTEOBLAST/CHONDROBLAST) form the polypeptide precursors of the collagen molecule
-->After **enzymatic modification**, MATURE COLLAGEN aggregate to become CROSS-LINKED in the formation of collagen fibers
35.
General Features of Collagen: -->Are the most ABUNDANT PROTEINS in the body
-->Found in connective tissue where tensile strength is needed
-->Major Examples:
1)Skin
2)Tendons
3)Cartilage
4)Bone
-->Forms the matrix/cement material in bone
-->Is formed from TROPOCOLLAGEN subunits
1)The TRIPLE HELIX IN TROPOCOLLAGEN is highly extended & strong, WITH many features (see below)
36.
General Features of Elastin: -->A FIBROUS PROTEIN in the CONNECTIVE TISSUE that contains elastic properties that allow tissues in th body to resume their shape after STETCHING OR CONTRACTION
-->Considered a "Load-Bearing" Tissue in vertebrates due to its ability to be used in places where MECHANICAL ENERGY is required to be stored
-->Encoded by the ELN gene
-->Polypeptide chain of elastin is rich in alanine & branched chain AA (valine, leucine, & isoleucine)
1)***Contains LITTLE hydroxyproline or hydroxylysine
-->Contains frequent LYSINE side chains, which can be involved in cross-links
1)***Cross links PREVENT the elastin fibers from being extended indefinitely
-->Is clinically relevant in 2 MAJOR CASES:
1)Cardiovascular Disease
2)Lung Emphysema
37.
General Features of Fibrous Proteins: -->The MAJORITY are STRUCTURAL PROTEINS; Have a high α-helix or β-sheet content
-->Major examples:
1)***Collagen
2)***Elastin
3)Keratin
4)Fibroin (insoluble protein in silk and other insect fibers)
-->Are often mechanically STRONG & HIGHLY CROSS-LINKED
-->Usually **INSOLUBLE**
-->Contain a high amt. of AA with NON-BULKY SIDE CHAINS (Ex. Glycine, Alanine, Serine, Glutamate, Glutamine)
38.
Genetics of Marfan Syndrome: -->Mutation is located on the FIBRILLIN-1 gene:
1)Syntheses Fibrillin, a major building block of microfibrils
2) Fibrilin constituites the struc. components of the suspensory ligament of the LENS
3)**Fibrillin serves as a substrate for ELASTIN in the aorta & other connective tissues **
-->Inherited as an AUTOSOMAL DOMINANT trait
-->Parent with the disease has a 50% chance of passing the dom. gene to the offspring
-->25% of cases have NO family history & are spontaneous mutations
-->Races & sexes are affected EQUALLY
-->Mutation is located on chromosome 15q21.1 (long arm of chrom. 15, region 2, band 1.1)
39.
Hole Regions: -->40nm gaps betwn adj. tropocollagens that contain carbohydrates
-->Thought to be **NUCLEATION SITES** for bone formation (i.e. site of polymerization)
40.
Major Types of Collagen in the Body: -->While collagen is in many places in the body, over 90% is in the form of Collagen Type I
-->Five Major Types:
1)Collagen Type I ("Be So Totally Cool"):
-->***Found in 'B'one, 'S'kin, 'T'endon, 'C'ornea
-->Other high yield areas: Dentin, fascia, & late wound repair
2)Collagen Type II
-->***Found mainly in Hyaline & Elastic Cartilage
-->Other areas: Vitreous humor of eye, Nucleus Pulposes
3)Collagen Type III
-->***Found mainly in the Reticular Fibers
-->Examples: Skin, BV's, Uterus, Fetal Tissue, Granulation Tissue
4)Collagen Type IV
-->***Found in the basement membrane/basal lamina
5)Collagen Type V
-->***Found in PLACENTA, HAIR, & cell surfaces
41.
Marfan Syndrome: -->A CONNECTIVE TISSUE disorder characterized by IMPAIRED STRUCTURAL INTEGRITY in many body systems, including:
1)Skeleton
2)Cardiovascular System
3)Eye
-->Is caused by the ABNORMAL FIBRILLIN PROTEIN being incorporated into the microfibrils along with the NORMAL fibrillin
1)Results in the INHIBITION of functional microfibrils
-->Considered the **MOST COMMON** single-gene malformation syndromes
42.
Osteogenesis Imperfecta Congenita (Type II OI): -->Is the MOST SEVERE form of OI; Is present either BEFORE or AT BIRTH; Is usually FATAL
-->Is due to a **mutation** in the gene involved in the assembly of the pro-α chains during the synthesis of PROCOLLAGEN (Ex. replacement glycine residues with AA's with bulky side chains)
-->The abnormal pro-α chains prevent the formation of procollagen triple-helical conformation
43.
Osteogenesis Imperfecta Tarda (Type I OI): -->Is the LESS SEVERE form of OI; Is often not present at birth
-->Is due to ***decreased production of α-chains (α-1 & α-2)
-->Presents in EARLY CHILDHOOD with fractures secondary to minor trauma
1)May be suspected if pre-natal ultrasound detects bowing or fractures of long bones
44.
Role of α1-AT in the lungs: -->Prevents the destruction of elastin in the alveolar walls by elastase
-->If α1-AT is non-functional, the destruction of the CT tissue by elastase can lead to **EMPHYSEMA***
45.
Role of α1-AT methioine: -->An AA residue that is REQUIRED to for the binding of α1-AT to its target protease
46.
Step that Osteogenesis Imperfecta inhibits in biosynthesis of collagen: -->At the formation of the triple collagen of PROCOLLAGEN from the glycoylated prepro-α-collagen
47.
Step that Scurvy inhibits in biosynthesis of collagen: **Hydroxylation of specific proline & lysine residues**
48.
Structure of Collagen: -->Collagen is rich in 2 AA: **PROLINE & GLYCINE**:
1)**1 out of 3 residues** are Glycine
2)Proline amt. is HIGH due to its involvement in HYDROYLATION RXN's
-->Many modified AA's are present in Collagen (***See three major exampls's below)
49.
Treatment of α1-AT: -->Can be reversed with WEEKLY treatment of an IV of α1-AT
1)Protein diffuses from the blood to the lung to initiate its therapeutic effect in fluid surrounding the epithelial cells of the lung
50.
Tropocollagen: -->The basic unit of collagen
-->Composed of TRIPLE HELIX of 3 polypeptide chains (~1000 residues in length)
51.
What is the first processing rxn in the biosynthesis & assembly of collagen?: -->The removal of the signal peptide that was attached to the collagen precusor (containing N & C terminal extensions
52.
α1-Antitrypsin (α1-AT or α1-Antiproteinase): -->A protein that inhibits many proteolytic enzymes that hydrolyze & destroy proteins
1)Well-known for its inhibitory affect on the neutrophil ELASTASE
-->Most of the α1-AT found in plasma is synthesized in the LIVER
1)Remainder is syn. in regions that are need the inhibitory action against elastase (Ex. Monocytes, Alveolar Macrophages)
