lecture 23 - fibroin and fibrous proteins summary

Question 1

fibroin is commonly reffered to as:

Answer 1

spider silk

Question 2

what are the characteristics of fibroin?

Answer 2

beta structure with extended strands and sheets

Question 3

explain the primary structure of fibroin

Answer 3

rich in ala and gly

Question 4

explain the secondary structure of fibroin

Answer 4

beta sheets

Question 5

explain the tertiary structure of fibroin

Answer 5

same as secondary

Question 6

explain the quaternary structure of fibroin

Answer 6

• multiple beta strands form sheets and sheets also stack together
• beta strands are held together by hbonds
• beta sheets are stacked via hydrophobic interactions
• interdigitation of small R-groups allows for very tight packing of beta sheets
• 3.5A btwn H, 5.0A btwn R groups
• extended beta structure means there is no real stretching capacity
• structure is very flexible and very strong (one sheet can shift relative to its neighbours) - allows bending of sheets

Question 7

summarize alpha keratin proteins

Answer 7

• 2 alpha helices forming a left handed coiled coil
• heptad repeats
• elasticity
• hair/nails

Question 8

summarize collagen proteins

Answer 8

• 3 left handed helices form right handed coil
• G-X-Y
• rigid
• CT

Question 9

summarize fibroin proteins

Answer 9

• b-strands forming stacked beta sheets
• ala-gly-
• strong but flexible

Question 10

all fibrous proteins are families of sequence with similar function, T or F? why?

Answer 10

• true
• all have other aa residue types that affect structure and function
• variations in sequences within a family give rise to differences in structural properties, and thus, functions