trbC

trbC is a gene name used in the annotation of several bacterial conjugative plasmids. The designation “trb” refers to transfer-related genes associated with the plasmid’s conjugation machinery, and trbC is typically placed within the trb transfer region, often near other trb genes and sometimes adjacent to the tra region.

In many plasmids, the trb operon encodes components of the mating pair formation (MPF) complex, which is part of the type IV secretion system responsible for transfer of plasmid DNA to recipient cells during conjugation. The exact role of trbC, however, varies across plasmid families and is not uniformly defined. In some annotations it is predicted to encode a small protein that participates in the assembly or stabilization of the transfer apparatus, while in others it is labeled as a hypothetical protein with no experimentally confirmed function.

Conservation of trbC homologs is observed across a range of conjugative plasmids, but sequence similarity can be limited, and functional assignments are often inferred from genomic context rather than direct biochemical evidence. Because plasmid gene organization differs between plasmid families (for example among IncP, IncI, and IncW plasmids), the presence, naming, or exact function of trbC may differ accordingly.

Overall, trbC is understood as part of the genetic toolkit that enables horizontal gene transfer via conjugation, contributing to the dissemination of plasmids and associated traits. Its precise function is typically described as context-dependent and subject to validation in individual plasmid studies.

See also: conjugative plasmids, type IV secretion system, mating pair formation, trb operon, horizontal gene transfer.