Past exam of the biochemistry course of the University of Cambridge / 2025 / Paper 5 / Section 1 / 1 / r / Solution

V3 is a plausible responsive partner; V8 is less likely to show the same stimulation. V3 conserves the aligned S/E and S/Q pairs implicated by the V2 comparisons, whereas V8 differs at those positions. This supports a prediction of conserved recognition, not a conclusion that sequence identity guarantees the same kinetic response.

Other residues, protein folding, lipid bilayer orientation and partner compatibility matter too. In particular, comparing the aligned motifs is more informative here than comparing only the variable N-terminal tails. The prediction should be checked by equivalent functional comparisons, rather than inferred from the family names alone.