Genetic analysis of the T4 holin: timing and topology

Gene. 2001 Mar 7;265(1-2):25-36. doi: 10.1016/s0378-1119(01)00365-1.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkaline Phosphatase / genetics
  • Alkaline Phosphatase / metabolism
  • Alleles
  • Amino Acid Sequence
  • Bacteriolysis / genetics
  • Bacteriophage T4 / genetics*
  • Bacteriophage T4 / growth & development
  • Lac Operon / genetics
  • Molecular Sequence Data
  • Mutation
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Deletion
  • Sequence Homology, Amino Acid
  • Time Factors
  • Viral Proteins / genetics*
  • Viral Proteins / isolation & purification
  • Viral Proteins / metabolism
  • beta-Galactosidase / genetics
  • beta-Galactosidase / metabolism


  • Recombinant Fusion Proteins
  • Viral Proteins
  • holin t protein, Enterobacteria phage T4
  • Alkaline Phosphatase
  • beta-Galactosidase