The putative Orf4 of broad-host-range conjugative plasmid R446 could Be related to the H-NS family of bacterial nucleoid-associated proteins.

The iml determinant of IncM plasmid R446 was described initially as a short fragment of DNA causing (when cloned in multicopy plasmids) insensitivity to pilus-dependent bacteriophage lysis in bacteria harboring coresident IncM plasmids. We have performed a computational analysis of the iml determinant of IncM plasmid R446 and found that a potential polypeptide (Orf4) shows similarity to the H-NS family of nucleoid-associated modulators of gene expression. The predicted protein has a molecular weight of 16.3 kDa and an isoelectric point of 5.50. Orf4 is adjacent and upstream of Orf5, a potential polypeptide related to the Hha/YmoA/RmoA family of proteins which modulate bacterial virulence expression (Hha and YmoA) and R100 transfer (RmoA) in response to environmental conditions.
(Copyright 1999 Academic Press.)