Given below are protein domains and their binding specificities.

Column X	Column Y
Interaction domain	Binding site
A. SH2 domain	i. Phosphorylated tyrosine residue on receptors
B. SH3 domain	ii. Charged head groups of specific phosphoinositides on Plasma membrane
C. PH domain	iii. Short proline -rich amino acid sequence on proteins
D. PTB domain

Which one of the following options represents all correct matches between Column X and Column Y?​

Correct option is D

​

• A. SH2 domain

  • Binding Site: i. Phosphorylated tyrosine residue on receptors
    The SH2 (Src Homology 2) domain specifically binds to phosphorylated tyrosine residues, typically on tyrosine kinase receptors. This is a well-known interaction.

• B. SH3 domain

  • Binding Site: iii. Short proline-rich amino acid sequence on proteins
    The SH3 domain binds to proline-rich motifs found in many proteins, particularly those involved in signaling pathways.

• C. PH domain

  • Binding Site: ii. Charged head groups of specific phosphoinositides on plasma membrane
    The PH (Pleckstrin Homology) domain binds to the phosphoinositides, specifically the charged head groups of phosphoinositides on the plasma membrane.

• D. PTB domain

  • Binding Site: i. Phosphorylated tyrosine residue on receptors
    The PTB (Phosphotyrosine Binding) domain binds to phosphorylated tyrosine residues similar to the SH2 domain, but with different specificity and structural features.

Analysis of Options:

1. A-i, B-ii, C-iii, D-ii

   • Incorrect. This does not match the correct interactions between the domains and their binding sites.

2. A-i, B-ii, C-ii, D-i

   • Incorrect. The PH domain should bind to phosphoinositides, not to the second option here.

3. A-i, B-iii, C-i, D-ii

   • Incorrect. The PH domain binds to phosphoinositides, but the SH2 domain interacts with phosphorylated tyrosines.

4. A-i, B-iii, C-ii, D-i

   • Correct. This correctly matches:
     • SH2 domain (A) with phosphorylated tyrosine residue (i)
     • SH3 domain (B) with proline-rich amino acid sequences (iii)
     • PH domain (C) with phosphoinositides (ii)
     • PTB domain (D) with phosphorylated tyrosine residue (i)