Structure of phage protein BC1872 from Bacillus cereus, a singleton with new fold

Abstract

Phagelike and prophage elements appear in many sequenced bacterial genomes and may associate with functionally important characteristics such as serotype conversion, pathogenesis, and phage immunity.1 Some prophage genes may have a profound effect on the host and alter properties such as virulence of nonpathogenic hosts and increase virulence of pathogenic hosts.2 VSH-1 is an example of a phagelike element in Brachyspira spirochetes, which is a recognized mechanism for gene transfer between B. hyodysenteriae cells.3 Phages of this type are found to enter long-term relationships with their hosts by integrating their genome into the host chromosome and exist as autonomous linear prophages within the host genome. The genome of Bacillus cereus strain ATCC 14579/DSM 31 codes for a probacteriophage phBC6A51. The prophage region spans 61,395 base pairs and contains 75 ORFs, many of which are described as hypothetical proteins. It appears that the prophage provides some evolutionary advantage to the B. cereus; therefore, studies of its proteins are important. Because the protein structure can provide useful function information, determination of structures of these proteins are of high priority.4 We have determined the crystal structure of BC1872, a prophage phBC6A51 protein from B. cereus, by using the single-wavelength anomalous diffraction (SAD) method. The protein forms a β/α/β three-layer sandwich structure and represents a new protein fold. The functional unit of BC1872 appears to be homo-dimer, and this structure provides new information about possible functionality of the protein.