Genetic analysis of the T4 holin: Timing and topology

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56 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)25-36
Number of pages12
Issue number1-2
Publication statusPublished - Mar 7 2001
Externally publishedYes


  • Bacteriophage
  • Lysis
  • Lysis inhibition
  • Lysis-inhibition (LIN)

ASJC Scopus subject areas

  • Genetics


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