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CSB327H1 Lecture Notes - Lecture 3: Pepsin, Type I Collagen, Ultimate Tensile Strength

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coraleel39
10 Oct 2012
School
UTSG
Department
Cell and Systems Biology
Course
CSB327H1
Professor
Maurice Ringuette

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Document Summary

Covalent cross-link formation (collagen molecule collagen fibril: aldol cross-links between two modified lysine side chains. Intermolecular cross-links occur between the n-terminal and c-terminal telopeptide domains: aldol cross-links are catalyzed by an extracellular enzyme called lysyl oxidase (lo) Lys and ho-lys residues are deaminated by lysyl oxidase. Spontaneously forms aldol cross-link: pro-lo is cleaved into lo by bmp1, lysine cross-links in adult skin, cornea and sclera, ho-lysine cross links in bone, cartilage, ligament, tendon, embryonic skin, and most major internal connective tissues. Fibrillogenesis (collagen fibril collagen fiber: lateral interactions of adjacent collagen molecules are quarter staggered or displaced by 1 d (65-67 nm) period. 1 d is comprised of 0. 6 d (hole zone) and 0. 4 d (overlap zone) Function of hole zone: access to modifying enzymes such as lo, site of hydroxyapeptite (calcium-phosphate) crystal formation (mineralization, fibril flexibility. Creates striation appearance of collagen in em micrograph. Positive stain: binds to regions rich in polar amino acids.

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Related Questions

1. The level of protein structure that is stabilized primarilyby non-covalent interactions between the side chains within asingle polypeptide chain is refered to as its:

A) primary structure

B) secondary structure

C) tertiary structure

D) quaternary structure

E) none of the above

2. Collagen, a strong fibrous protein found in connectivetissue, bone, and the extracellular matrix, has a structure inwhich three left-handed helices wind around each other to form aright-handed triple helix. The primary structure of collagen has arepeat unit of -(Gly-X-Pro)- Which of the following bonds stabilizethe collagen triple helix? (mark all that apply)

A) Hydrogen bonds between hydroxyproline residues

B) Hydrogen bonds between N-H and C=O

C) Ionic bonds between amino acid side chains

D) Hydrogen bonds between charged amino acids

3. The non-covalent forces that stabilize the Beta-strandconformation of peptides include:

A) H-bonds between amide C=O and amide NH

B) Van der Waals packing between the peptide backbone atoms

C) Van der Waals packing due to side chain interdigitation

D) Only A and B above

E) None of the above

4. What is the approximate length difference of a 22-kDasingle-stranded ?-helical protein segment vs. a 22-kDasingle-stranded ?-strand protein segment? Assume a mean residuemass of 110 Da. Show work.


5. Circular dichroism measurements have shown that the peptidebackbone of poly-l-lysine (KKKKKKK) adopts a random coilconformation at pH 7.0, but becomes ?-helical as the pH is raisedabove 10. This observation is known as the

Qs. 3) Maligant cancer cells that have entered the bloodstream can imitate lymphocytes in exiting the bloodstream and entering underlying issues in the process of metastasis. This ‘lymphocyte mimicry’ can be summarized as….

A) An initial cadherin-dependent rolling followed by an integrin-dependent adhesion and emigration

B) An initial cadherin-dependent rolling followed by an I-CAM-dependent adhesion and emigration

C) An initial cadherin-dependent rolling followed by a selectin-dependent adhesion and emigration

D) An initial selectin-dependent rolling followed by a cadherin-dependent adhesion and emigration

E) An initial selectin-dependent rolling followed by an I-CAM-dependent adhesion and emigration

Qs. 4) Type IV collagen molecules can interact at their C-termini to form dimers and at their N-termini to form tetramers. What category do you think this type of collagen belongs to?

A) Fibrillar

B) Fibril-associated

C) Network-forming

D) Proteoglycan core

E) Anchorage fibril

Qs. 5) Which components of the extracellcular matrix are mostly responsible for its ability to resist compressive and tensile forces, respectivally?

A) Collagens and glycoproteins

B) Glycoproteins and collagens

C) Glycosaminoglycans and glycoproteins

D) Glycosaminoglycans and collagens

E) Collagens and glycosaminoglycans

Qs. 6) the size distribution of exons coding for collagen helical domains in various vertebrates reveals a unique pattern. This pattern provides clues to the evolutionary history of the genes encoding fibrillar collagen a chains. What is this pattern?

A) The length of most exons is a multiple of 100 nucleotides

B) Most exons code for 54, or a multiple of 54, Gly-X-Y repeats.

C) The length of most exons is a multiple of 30 nucleotides

D) Most exons code for 6, or a multiple of 6, Gly-X-Y repeats

E) None of the above

You propose experiments totest how penicillin brings about cell killing. Your starting pointis your recent finding that penicillin inhibits the enzyme thatcross-links between different strands of the peptidoglycan thatforms the principal component of the bacterial cell wall. Youformulate a hypothesis based on an analogy between the bacterialand plant cell wall and on the concept of turgor pressure.Summarize the hypothesis and an experiment to test it.