B3 Tc structure

Question 1

describe structure of TCR

Answer 1

Disulfide-linked heterodimer, each chain contains: antibody C- like domain & antibody ((like fab) the juxtaposition of the V domains forms the site for antigen recognition. (TCR resembles a membrane-bound Fab fragment)

Question 2

Describe (antibody) fab region

Answer 2

Fab fragment is a disulfide-linked heterodimer, each chain of which contains one antibody C domain and one V domain; the juxtaposition of the V domains forms the antigen-binding site.

Question 3

how do Tc interact with antigen (recognition)

Answer 3

Tc interact w/ short continuous a.a. sequences (may be buried w/in protein)
Proteins need to be unfolded & digested into fragments to be recognised by Tc.
Tc recognise fragments only when presented by MHC molecules

(Tc recognise peptide fragment not antigenic protein)

Question 4

describe MHC-1

Answer 4

8-10a.a.
highly conserved: cluster Y residues
form H bonds to a.a terminus of bound peptide
A 2nd cluster of residues form H-bonds & ionic interactions w/ peptide backbone @ C terminus.

Question 5

MHC-II

Answer 5

13a.a
peptide bind by interactions along length of binding groove
e.g. H-bonds along length.

Question 6

How do peptides bind MHC molecules

Answer 6

Through structurally related anchor molecules

Question 7

where are Tc developed

Answer 7

Thymus: the TCRa & B chains are composed of discrete segments joined by somatic recombination (during development)

Question 8

what does RAG aid the generation of

Answer 8

alpha & beta chains

Question 9

RSS flank what

Answer 9

RSS: recombination signal sequences
flank gene segments.
individual segments of TCRa & TCRB are flanked by heptamer spacer nonamer RSS
(joining of gene segments follows 12/13 rule.)

Question 10

what allows joining of VBeta & JBeta

Answer 10

direct joining is allowed by 12/13 rule.