Identification of the new protein participating in the archaea motility regulation

A new family of archaeal proteins, CheM, having no homologues among bacteria and eukaryotes, was identified. Genes cheM are represented only in archaea possessing the chemotaxis and generally located close to che and fla loci. There is only one copy of the cheM gene in thermophilic and methanogenic archaea. Halophilic archaea have an additional paralog of the cheM gene. Mutant strains of Halobacterium salinarum R1 with deletions of the cheM1 (OE2402F) and cheM2 (OE2404R) genes were obtained. Mutant strains were not differ from the wild type strain by speed of movement in liquid medium but had appreciable differences in the diameter of a swarm on semi-liquid agar, indicative of reduced chemotaxis. It was demonstrated that the CheM2 protein from H. salinarum R1 co-isolates with protein CheY, the chemotaxis regulator in the conditions of its activation. The specific interaction between proteins CheM and CheY from hyperthermophilic archaea Pyrococcus horikoshii OT3 was also found. We suppose that CheM proteins provide adaptation of the chemotaxis system universal for bacteria and archaea to the specific archaeal flagellar motor apparatus.