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The putative peptide antibiotic-like killing factor (SdpC) exporter, SdpAB. However, Pérez Morales et al. 2013 concluded that SdpAB are not required for secretion, translation, or stability of SdpC, and that they may participate in a posttranslation step in the production of SDP. The mature form of the SDP toxin contains a disulfide bond. Their data indicate that while the disulfide bond does increase activity of SDP, it is not essential for SDP activity, and that the disulfide bond is formed independently of SdpAB. Thus, SDP production is a multistep process in which SdpAB are required for SDP production, likely by controlling, directly or indirectly, cleavage of SDP from the pro-SdpC precursor (Pérez Morales et al. 2013).

SdpAB of Bacillus subtilis
SdpA (YvaW) (CAB15380)
SdpB (YvaX) (CAB15381)

YvaB homologue of 436 aas and 10 or 11 TMSs.  It is encoded by a gene that is adjacent to one that probably codes for an outer membrane porin with TC# 1.B.89.1.21.

SdpB homologue of Streptomyces coelicolor

Two component uncharacterized homologues of SdpB (YvaX) of 287 aas and 308 aas, respectively, both with 6 TMSs.  Their genes are adjacent to each other but transcribed devergently.  According to GO, they may be γ-glutamyl carboxylases or peptidyl glutamate carboxylases.  Two other such homologues are encoded in the same genome (see 9.A.31.1.5).


SdpB1/2 of Bdellovibrio bacteriovorus
SdpB1, 287 aas; 6 TMSs
SdpB2, 308 aas; 6 TM

YitOP, a probable two component YIT killer factor (TC# 9.B.139.1.6) export system (Kobayashi and Ikemoto 2019).

YitOP of Bacillus subtilis
YitO, 309 aas and 6 TMSs, O06750
YitP, 178 aas and 1 TMS, N-terminal, O06751

Putative transporter consisting of two HTTM domain-containing proteins of 299 aas and 6 TMSs as well as 291 and possibly 7 or 8 TMSs.  These two proteins are homologous to each other and the two proteins with TC# 9.A.31.1.2.

Putative two component transporter of Bdellovibrio bacteriovorus