title: Characterization and determination of holin protein of Streptococcus suis bacteriophage SMP in heterologous host.
abstract: BACKGROUND
  Holins are a group of phage-encoded membrane proteins that control access of phage-encoded endolysins to the peptidoglycan, and thereby trigger the lysis process at a precise time point as the 'lysis clock'. SMP is an isolated and characterized Streptococcus suis lytic phage. The aims of this study were to determine the holin gene, HolSMP, in the genome of SMP, and characterized the function of holin, HolSMP, in phage infection.
  
  
  RESULTS
  HolSMP was predicted to encode a small membrane protein with three hydrophobic transmembrane helices. During SMP infections, HolSMP was transcribed as a late gene and HolSMP accumulated harmlessly in the cell membrane before host cell lysis. Expression of HolSMP in Escherichia coli induced an increase in cytoplasmic membrane permeability, an inhibition of host cell growth and significant cell lysis in the presence of LySMP, the endolysin of phage SMP. HolSMP was prematurely triggered by the addition of energy poison to the medium. HolSMP complemented the defective λ S allele in a non-suppressing Escherichia coli strain to produce phage plaques.
  
  
  CONCLUSIONS
  Our results suggest that HolSMP is the holin protein of phage SMP and a two-step lysis system exists in SMP.
authors.affiliation: Department of Animal Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai Key Laboratory of Veterinary Biotechnology, 800 Dongchuan Road, Shanghai, People's Republic of China.
authors.forename: Yibo
authors.initials: Y
authors.lastname: Shi
authors.forename: Yaxian
authors.initials: Y
authors.lastname: Yan
authors.forename: Wenhui
authors.initials: W
authors.lastname: Ji
authors.forename: Bin
authors.initials: B
authors.lastname: Du
authors.forename: Xiangpeng
authors.initials: X
authors.lastname: Meng
authors.forename: Hengan
authors.initials: H
authors.lastname: Wang
authors.forename: Jianhe
authors.initials: J
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D001433:Bacteriolysis; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D017108:Streptococcus Phages / Q000235:genetics* / Q000502:physiology*; D017011:Streptococcus suis / Q000821:virology; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D014764:Viral Proteins