1.E.57 The Actinobacterial Phage Holin (APH) Family
The mycobacteriophage Ms6 is a temperate double-stranded DNA (dsDNA) bacteriophage which, in addition to the predicted endolysin (LysA)-holin (Gp4) lysis system, encodes three additional proteins within its lysis module: Gp1, LysB, and Gp5. Ms6 Gp4 (TC# 1.E.18.1.2) was previously described as a class II holin-like protein. By analysis of the amino acid sequence of Gp4, an N-terminal signal-arrest-release (SAR) domain was identified, followed by a typical transmembrane domain (TMD), features which had previously been observed for pinholins. A second putative holin gene (gp5) encoding a protein with a predicted single N-terminal TMS was identified at the end of the Ms6 lytic operon. Neither the putative class II holin nor the single TMS polypeptide could trigger lysis in pairwise combinations with the endolysin LysA in Escherichia coli (Catalão et al. 2011). One-step growth curves and single-burst-size experiments of different Ms6 derivatives with deletions in different regions of the lysis operon demonstrated that the gene products of gp4 and gp5, although nonessential for phage viability, appear to play a role in controlling the timing of lysis: an Ms6 mutant with a deletion of gp4 (Ms6(Δgp4)) caused slightly accelerated lysis, whereas an Ms6(Δgp5) deletion mutant delayed lysis, which is consistent with holin function. Additionally, cross-linking experiments showed that Ms6 Gp4 and Gp5 oligomerize and that both proteins interact. These results suggest that in Ms6 infection, the correct and programmed timing of lysis is achieved by the combined action of Gp4 and Gp5 (Catalão et al. 2011).
Mycobacteriophage Ms6 Gp5 holin of 124 aas and 1 N-terminal TMS (of the DUF2746/Pha00327 family) (Catalão et al. 2011).
Gp5 holin of Mycobacteriophage Ms6
Gp32 of Mycobacteriophage Che12 of 108 aas and 1 TMS.
Gp32 of Mycobacerial phage Che12
Putative holin of 110 aas and 1 N-terminal TMS.
Putative holin of Leifsonii xyli
Putative holin of 117 aas and 1 TMS, Gp33
Gp33 of Mycobacterial phage DS6A
Putative holin of 129 aas and 1 TMS
Putative holin of Gordonia sihwensis
Putative holin of 157 aas and 1 TMS
Holin of Acinomyces turicensis
Putative holin of 146 aas and 1 TMS, Gp26
Gp26 of Tsukamurella phage TPA2
Putative holin of 145 aas and 1 TMS
Holin of Gordonia phage GTE5
Putative holin of 139 aas and 1 TMS
Holin of Gordonia sihwensis
Putative holin of 122 aas and 1 TMS
Holin of Segniliparus rugosus
Putative holin of 117 aas and 1 TMS
Hoin of Rhodocuccus opacus
Putative holin of 173 aas and 1 TMS
Holin of Corynebacterium callunae
Putative holin of 140 aas and 1 TMS
Holin of Corynebacterium aurimucosum (Corynebacterium nigricans)
Putative holin of 118 aas and 1 TMS
Holin of Corynebacterium pyruviciproducens