P35 holin family

The PRD1 Phage P35 Holin (P35 Holin) Family (TC# 1.E.5) is a member of Holin Superfamily III.[1] The prototype for this family is the lipid-containing PRD1 enterobacterial phage holin protein P35 (12.8 kDa; TC# 1.E.5.1.1) encoded by gene XXXV (orfT).[2] It is a component of a typical holin-endolysin system which functions to lyse the host bacterial cell.

Structure

P35 holin (TC# 1.E.5.1.1) has 3 transmembrane segments (TMSs) with 5 positively charged residues between TMSs 1 and 2. It has 4 positively charged residues at the C-terminus.[2] It is therefore thought that the N-terminus is in the periplasm and the C-terminus is in the cytoplasm. Homologues of 109 amino acyl residues (aas), which also have 3 putative TMSs, are encoded in the genomes of Xylella fastidiosa strains.[2]

Function

PRD1 infects gram-negative cells harboring a conjugative IncP plasmid. Progeny phage particles are released from the host cell via a two-component lysis system (holin-endolysin). Ziedaite et al. (2005) monitored the ion flux and ATP content of infected cells to set up a model of the sequence of lysis-related physiological changes in the infected host. They showed a decrease in the intracellular level of ATP is the earliest indicator of cell lysis, followed by the leakage of K+ from the cytosol approximately 20 minutes prior to the decrease in culture turbidity. However, the K+ efflux did not immediately lead to the depolarization of the cytoplasmic membrane or leakage of the intracellular ATP. These effects were observed only approximately 5 to 10 minutes prior to cell lysis.[3] Similar results were obtained using cells expressing the holin and endolysin genes from plasmids.

The reaction catalyzed by P35 holin is:

autolysin (in) → autolysin (out)

See Also

References

  1. ↑ Reddy, Bhaskara L.; Saier, Milton H. (2013-11-01). "Topological and phylogenetic analyses of bacterial holin families and superfamilies". Biochimica Et Biophysica Acta 1828 (11): 2654–2671. doi:10.1016/j.bbamem.2013.07.004. ISSN 0006-3002. PMC 3788059. PMID 23856191.
  2. 1 2 3 Rydman, Pia S.; Bamford, Dennis H. (2003-07-01). "Identification and mutational analysis of bacteriophage PRD1 holin protein P35". Journal of Bacteriology 185 (13): 3795–3803. ISSN 0021-9193. PMC 161566. PMID 12813073.
  3. ↑ Žiedaitė, Gabija; Daugelavičius, Rimantas; Bamford, Jaana K. H.; Bamford, Dennis H. (2005-08-01). "The Holin Protein of Bacteriophage PRD1 Forms a Pore for Small-Molecule and Endolysin Translocation". Journal of Bacteriology 187 (15): 5397–5405. doi:10.1128/JB.187.15.5397-5405.2005. ISSN 0021-9193. PMC 1196050. PMID 16030234.

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