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.

Characterization of Lipoteichoic Acids asLactobacillus delbrueckiiPhage Receptor Components

“…We have previously suggested that there are at least three types of receptors for L. delbrueckii phages: two specific for LL-H and its host range mutant LL-H-a21 and one specific for the phage JCL1032 (23). In this study, we demonstrate that these L. delbrueckii phages are inactivated by purified LTAs from L. delbrueckii subsp.…”

“…As far as we know, LL-H-a21 differs from LL-H only by a single amino acid in the receptor binding protein Gp71, thus suggesting that the specificity of inactivation reactions resides in the Gp71-LTA interaction (23). Like LL-H-a21, JCL1032 reacted with the LTAs examined in this study, although more LTAs were needed for significant inactivation.…”

“…Ads-5, one of the LL-H-resistant mutants of L. delbrueckii subsp. lactis ATCC 15808, is able to block the adsorption of LL-H but not the adsorption of the LL-H host range mutant LL-H-a21 or JCL1032 (23). In this study, we investigated if purified LTAs isolated from ATCC 15808 and Ads-5 could serve as a receptor substance in the early stage of L. delbrueckii phage infections.…”

“…Both phages have noncontractile tails, and their genetic determinants involved in host recognition have been characterized. Gp71 and its homolog ORF474 determine the adsorption specificities of LL-H and JCL1032, respectively (23). Ads-5, one of the LL-H-resistant mutants of L. delbrueckii subsp.…”

Molecular Interaction between Lipoteichoic Acids and Lactobacillus delbrueckii Phages Depends on d -Alanyl and α-Glucose Substitution of Poly(Glycerophosphate) Backbones

“…The LL-H gene product responsible for host recognition has been identified as Gp71 by utilizing the isolated LL-H-resistant mutant (Ads-5) of L. delbrueckii subsp. lactis ATCC 15808 and the LL-H host range mutants (35). The small isometric-headed phage LL-H, with a noncontractile tail, a baseplate, and a central tail fiber (5,21), exhibits only limited DNA similarity to another L. delbrueckii phage, JCL1032 (20,36).…”