Genetic analysis of the T4 holin: timing and topology.
The t protein of bacteriophage T4 shares with other holins the ability to cause the formation of a lethal membrane lesion which allows the phage endolysin to attack the peptidoglycan. Moreover, T, like other holins, acts in a saltatory manner at a precisely programmed time in the vegetative cycle. Unlike other holins, however, T has the unique ability to postpone its lethal function in response to a secondary infection by a T-even phage during the vegetative cycle. A signal transduction system that responds to the secondary infection is thought to be encoded by some of the numerous r genes, defined by mutations that abolish this lysis-inhibition (LIN) response. The primary structure of T differs from two main structural patterns found in more than 30 orthologous groups of holins. Genetic approaches were taken to probe the t sequence for features involved in membrane localization, functional timing and LIN regulation. Gene fusion analysis indicates that T has a single TMD near the N-terminus, with the bulk of the protein residing in the periplasm. Mapping and phenotypic analysis of deletion and point mutations in t indicates that the periplasmic domain of T is the major determinant of the timing mechanism and is involved in the LIN response.
Department of Biochemistry and Biophysics, 2128 TAMU, Texas A&M University, 77843-2128, College Station, TX, USA.
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Ramanculov
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Young
D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D001433:Bacteriolysis / Q000235:genetics; D017122:Bacteriophage T4 / Q000235:genetics* / Q000254:growth & development; D007763:Lac Operon / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014764:Viral Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; C120332:holin t protein, Enterobacteria phage T4; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase