SEQUENCE-ANALYSIS OF THE LYSIN GENE REGION OF THE PROLATE LACTOCOCCALBACTERIOPHAGE-C2

Approximately 80% of the genome of the prolate-headed lactococcal bact eriophage c2 was cloned into shuttle vectors pSA3 and pFX3 in Escheric hia coli and transferred to Lactococcus lactis. A 1.67-kilobase EcoRV fragment containing the gene for the phage lysin was identified and th e position and orientation of the phage lysin gene in the physical map of the phage were determined. The phage lysin was expressed in E. col i and its sequence was determined and compared with the sequences of o ther bacteriophage lytic genes. The sequence was similar, but not iden tical, to that of the related lactococcal phage m13, having a number o f silent substitutions and an apparent deletion that altered the carbo xy terminus of the protein. Possible alternative translation initiatio n codons for the lysin gene and two possible alternative mechanisms fo r access of the lysin enzyme to the cell wall are discussed. An open r eading frame upstream of the putative lysin gene was found to be 177 b ase pairs longer than that reported for phage m13. A codon usage table for the lysin genes of several phages as well as for reported gene se quences from L. lactis and lactococcal bacteriophages is presented.