Ribsomes

Question 1

How did CryoEM help get structural data

Answer 1

Low resolution molecular replacement structure
Can show gross conformational changes in ribsome states that may not all be able to be crystallised.
The peptidyl transferase center is located on the large 50S ribosomal subunit ≈20 Å below the subunit interface at the entry of the peptide tunnel that exits on the other side of the large subunit. High-resolution crystal structures of the 50S subunit have been reported together with different aminoacyl- and peptidyl-tRNA substrate analogs
(Exxtra Reading)

Question 2

Struture

Answer 2

2 different subunits
binding regions are almost all RNA
proteins- glob head and long tail

Question 3

Peptide Bond catalyses

Answer 3

peptidly transferase centre was observed to have no protein nearby so cannot catalyse reaction,
active site was made entirely of RNA(Ribosome is ribozyme)
Identified where the peptidly transferase site was(50s) and
CCA ends ninds to A and P site and therefore online RNA is in the position to facitlitate catalysis

Question 4

How is peptidly bond cataylsis done

Answer 4

model 3 RNA groups to form H bond with alpha-amino group (N=O)
A2486, two of interactions(OH and N3)
mutation of this produces reduction of rate and removal on dependance of pH
since the local enviroment may raise pKA of A2486 to function as a base via charge relay system

Question 5

Recognition of tRNA by 30s subunit

Answer 5

A1492&A1493