Functional assembly of the lambda S holin requires periplasmic localization of its N-terminus.
Bacteriophage-lambda-induced host-cell lysis requires two phage-encoded proteins, the S holin and the R transglycosylase. At a specific time during infection, the holin forms a lesion in the cytoplasmic membrane that permits access of the R protein to its substrate, the peptidoglycan. The lambda S gene represents the prototype of holin genes with a dual-start motif; they encode two proteins, a lysis effector and a lysis inhibitor. Although the two S proteins differ only by two amino acids (Met-1 and Lys-2) at the N-terminus, the longer product (S107) acts as an inhibitor of the lysis effector (S105). The functional difference between the proteins has been previously ascribed to the Lys-2 residue in S107. It was therefore of interest to determine the subcellular localization of the N-terminus of either S protein. To study the membrane topology of the S proteins, we used the topology probe TEM beta-lactamase and an N-terminal tag derived from the Pseudomonas aeruginosa phage Pf3 coat protein. We show that both S proteins have a type III (Nout/Cin) topology. The results provide insight into the regulatory mechanism imposed by the dual-start motif and will be discussed in terms of a model for temporal regulation of the S-dependent "hole" in the membrane.http://link.springer-ny. com/link/service/journals/00203/bibs/172n1p31.html
Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Dr. Bohrgasse 9, A-1030 Vienna, Austria.
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D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000737:chemistry / Q000502:physiology*; D015153:Blotting, Western; D005814:Genes, Viral; D008969:Molecular Sequence Data; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics
C108624:S holin, bacteriophage lambda; D014764:Viral Proteins