TABLE 1.

Envelope proteins that copurified with LbcA and were also isolated by an LbcA-CtpA-S302A protease trap^a

Protein	Predicted feature or function	Abundance rank with LbcAb	Abundance rank with LbcA-CtpA trapc	CtpA substrate of Srivastava et al.d
PA1198	Peptidoglycan NlpC/P60 endopeptidase	3	2	Yes
PA1048	Peptidoglycan-binding OmpA C-terminal domain	4	7	NT
RlpA	Peptidoglycan lytic transglycosylase	5	4	No
MltD	Peptidoglycan lytic transglycosylase	10	3	No
MltB1	Peptidoglycan lytic transglycosylase	13	6	NT
MepM	Peptidoglycan LytM/M23 endopeptidase	18	1	Yes
AmiB	Peptidoglycan amidase	65	23	NT

^aCell envelope proteins that copurified with LbcA-CtpA-S302A, but not with LbcA-CtpA, following in vivo cross-linking (17) and also copurified with LbcA-FLAG from a ctpA-S302A strain in this study with average peptide spectral matches ≥5-fold higher than those in an LbcA no-FLAG-tag negative-control purification (see Tables S4 to S6 in the supplemental material).

^bRank based on the average number of peptide spectral matches among 67 cell envelope proteins that copurified with LbcA-FLAG (Table S6).

^cRank based on the average number of peptide spectral matches among 25 cell envelope proteins that copurified exclusively with the LbcA-CtpA-S302A trap (17).

^dIn the study by Srivastava et al., a protein was classified as a CtpA substrate if a FLAG-tagged version accumulated in a ΔctpA mutant in vivo and the protein was degraded by CtpA in vitro (17). NT, not tested by Srivastava et al.