Geukens N, Lammertyn E, Van Mellaert L, Schacht S, Schaerlaekens K, Parro V, Bron S, Engelborghs Y, Mellado RP, Anné J. Membrane topology of the Streptomyces lividans type I signal peptidases.
J Bacteriol 2001;
183:4752-60. [PMID:
11466278 PMCID:
PMC99529 DOI:
10.1128/jb.183.16.4752-4760.2001]
[Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2000] [Accepted: 05/26/2001] [Indexed: 11/20/2022] Open
Abstract
Most bacterial membranes contain one or two type I signal peptidases (SPases) for the removal of signal peptides from export proteins. For Streptomyces lividans, four different type I SPases (denoted SipW, SipX, SipY, and SipZ) were previously described. In this communication, we report the experimental determination of the membrane topology of these SPases. A protease protection assay of SPase tendamistat fusions confirmed the presence of the N- as well as the C-terminal transmembrane anchor for SipY. SipX and SipZ have a predicted topology similar to that of SipY. These three S. lividans SPases are currently the only known prokaryotic-type type I SPases of gram-positive bacteria with a C-terminal transmembrane anchor, thereby establishing a new subclass of type I SPases. In contrast, S. lividans SipW contains only the N-terminal transmembrane segment, similar to most type I SPases of gram-positive bacteria. Functional analysis showed that the C-terminal transmembrane anchor of SipY is important to enhance the processing activity, both in vitro as well as in vivo. Moreover, for the S. lividans SPases, a relation seems to exist between the presence or absence of the C-terminal anchor and the relative contributions to the total SPase processing activity in the cell. SipY and SipZ, two SPases with a C-terminal anchor, were shown to be of major importance to the cell. Accordingly, for SipW, missing the C-terminal anchor, a minor role in preprotein processing was found.
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