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Which functional group participates in disulphide bond formation in proteins :-
A
Thioether
B
Thiol
C
Thioester
D
Thiolactone
Detailed Solution
A disulphide bond (-S-S-) is formed by the oxidation of two thiol (-SH) groups.
In proteins the thiol groups belong to the side chains of cysteine residues.
$R-SH + HS-R' \xrightarrow{[O]} R-S-S-R' + 2[H]$
Two cysteine residues joined in this way form cystine; such disulphide bridges hold different parts of a polypeptide chain (or different chains) together and stabilise the tertiary and quaternary structure, for example in insulin and keratin.
Methionine contains a thioether group, which does not form disulphide bonds.
So the functional group is the thiol group.
In proteins the thiol groups belong to the side chains of cysteine residues.
$R-SH + HS-R' \xrightarrow{[O]} R-S-S-R' + 2[H]$
Two cysteine residues joined in this way form cystine; such disulphide bridges hold different parts of a polypeptide chain (or different chains) together and stabilise the tertiary and quaternary structure, for example in insulin and keratin.
Methionine contains a thioether group, which does not form disulphide bonds.
So the functional group is the thiol group.