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 Inc M plasmids. We have performed a computational analysis of the iml determina nt of IncM plasmid R446 and found that a potential polypeptide (Orf4) shows similarity to the H-NS family of nucleoid-associated modulators of gene ex pression. The predicted protein has a molecular weight of 16.3 kDa and an i soelectric point of 5.50. Orf4 is adjacent and upstream of Orf5, a potentia l polypeptide related to the Hha/YmoA/RmoA family of proteins which modulat e bacterial virulence expression (Hha and YmoA) and R100 transfer (RmoA) in response to environmental conditions, (C) 1999 Academic Press.