Ydiv

YdiV is a bacterial regulatory protein encoded by the ydiV gene in several Gram-negative bacteria, most notably Escherichia coli and related enteric species. It functions as a negative regulator of the flagellar gene regulatory cascade by modulating the activity of the FlhD4C2 master regulator that initiates flagellar gene expression. Through its action, YdiV reduces the production of flagellar components and bacterial motility.

Mechanism: YdiV physically associates with FlhD and FlhC, the components of FlhD4C2, inhibiting the complex's ability to activate class II flagellar operons. In some bacteria, YdiV also promotes turnover of FlhD4C2 via the ClpXP protease, lowering FlhD4C2 levels and further suppressing motility.

Physiological significance: By tuning flagellar synthesis, YdiV helps align motility with environmental conditions, energy availability, and cellular state. Changes in YdiV activity can influence biofilm formation, surface attachment, and colonization traits in certain pathogens.

Genetics and distribution: The ydiV gene is commonly located near motility-related genes and is conserved among Enterobacteriaceae. YdiV belongs to a family of regulatory proteins that act as antagonists of FlhD4C2, and several species harbor distinct YdiV homologs with similar function.

See also: FlhD, FlhC, ClpXP.