title: A conserved C-terminal region in Gp71 of the small isometric-head phage LL-H and ORF474 of the prolate-head phage JCL1032 is implicated in specificity of adsorption of phage to its host, Lactobacillus delbrueckii.
abstract: Thirty-five phage-resistant mutants of Lactobacillus delbrueckii subsp. lactis ATCC 15808 were selected. Thirty-three of these mutants were assigned to the Bes group, while the remaining two were grouped under the Ads designation. Bes group mutants adsorbed phage LL-H but did not allow efficient phage development. Preliminary evidence suggests that these strains exhibit a mutation that changes the DNA specificity of a restriction-modification system. The Ads group mutants did not adsorb the small isometric-head phage LL-H. The results suggest that there are at least three different types of phage receptors in L. delbrueckii: two that are specific for small isometric-head phages and one that is specific for prolate-head phage JCL1032. Five LL-H host-range mutants which could overcome the adsorption block (a-type mutants) were selected and investigated by sequencing the genes g71 and g17, which encode minor and major tail proteins, respectively. Each of the a-type mutants carried a nucleotide change at the 3' end of gene g71. No mutations were observed in gene g17. Comparison of the gene product of g71 of phage LL-H with its homolog in JCL1032 (ORF474) showed that these proteins had very similar C-terminal regions. No similarities were found at the N-terminal part of the proteins. We conclude that the C-terminal portion of the protein encoded by g71 of phage LL-H and its homolog in phage JCL1032 determines the adsorption specificities of these phages on L. delbrueckii.
authors.affiliation: Department of Biology, University of Oulu, FIN-90014 Oulu, Finland.
authors.forename: Victor
authors.initials: V
authors.lastname: Ravin
authors.forename: Liisa
authors.initials: L
authors.lastname: Räisänen
authors.forename: Tapani
authors.initials: T
authors.lastname: Alatossava
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D007777:Lactobacillaceae / Q000235:genetics / Q000821:virology*; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D016415:Sequence Alignment; D013045:Species Specificity; D014764:Viral Proteins / Q000235:genetics; D014779:Virus Replication
chemical_list: D014764:Viral Proteins