The Phage T4 Antiholin RI Has a Cleavable Signal Peptide, Not a SAR Domain

verfasst von

Denise Mehner-Breitfeld, Jan Michel Frederik Schwarzkopf, Ry Young, Kiran Kondabagil, Thomas Brüser

Abstract

Holin/endolysin-mediated lysis of phage T4 of Escherichia coli is tightly regulated by the antiholins RI and RIII. While regulation by the cytoplasmic RIII plays a minor role, the periplasmic antiholin RI binds tightly to the holin T and is believed to directly sense periplasmic phage DNA from superinfections as a trigger for the inhibition of lysis. RI has been reported to contain a non-cleavable signal peptide that anchors the protein to the membrane. Lysis is believed to be induced at some stage by a membrane depolarization that causes a release of RI into the periplasm without cleavage of the signal anchor. For the current model of phage lysis induction, it is thus a fundamental assumption that the N-terminal trans-membrane domain (TMD) of RI is such a signal anchor release (SAR) domain. Here we show that, in contrast to previous reports, this domain of RI is a cleavable signal peptide. RI is processed and released into the periplasm as a mature protein, and inactivation of its signal peptidase cleavage site blocks processing and membrane release. The signal peptide of RI can also mediate the normal translocation of a well-characterized Sec substrate, PhoA, into the periplasm. This simplifies the current view of phage lysis regulation and suggests a fundamentally different interpretation of the recently published structure of the soluble domains of the RI–T complex.

Organisationseinheit(en)

Institut für Mikrobiologie

Externe Organisation(en)

Texas A and M University
Indian Institute of Technology Bombay (IITB)

Typ

Artikel

Journal

Frontiers in Microbiology

Band

12

Anzahl der Seiten

8

ISSN

1664-302X

Publikationsdatum

11.08.2021

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Mikrobiologie (medizinisch), Mikrobiologie

Fachgebiet (basierend auf ÖFOS 2012)

Biochemie

Elektronische Version(en)

https://doi.org/10.3389/fmicb.2021.712460 (Zugang: Offen)