A residue located at the junction of the head and stalk regions of measles virus fusion protein regulates membrane fusion by controlling conformational stability.

The fusion (F) protein of measles virus performs refolding from the thermodynamically metastable prefusion form to the highly stable postfusion form via an activated unstable intermediate stage, to induce membrane fusion. Some amino acids involved in the fusion regulation cluster in the heptad repeat B (HR-B) domain of the stalk region, among which substitution of residue 465 by various amino acids revealed that fusion activity correlates well with its side chain length from the Cα (P<0.01) and van der Waals volume (P<0.

Intramolecular complementation of measles virus fusion protein stability confers cell-cell fusion activity at 37 °C.

The fusion (F) protein of measles virus mediates membrane fusion. In this study, we investigated the molecular basis of the cell-cell fusion activity of the F protein. The N465H substitution in the heptad repeat B domain of the stalk region of the F protein eliminates this activity, but an additional mutation in the DIII domain of the head region - N183D, F217L, P219S, I225T or G240R - restores cell-cell fusion.