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. Author manuscript; available in PMC: 2026 Jul 18.
Published in final edited form as: Nat Chem. 2025 Jul 18;17(9):1371–1382. doi: 10.1038/s41557-025-01871-3

Figure 4. Natural MccA/MccB diversity encompasses orthogonal enzymes for C-terminal protein modification.

Figure 4.

(A) A positional scanning peptide library revealed that MccB is an epitope-specific enzyme. (B) The MccB enzyme family harbors numerous homologs that act on substrates distinct from E. coli MccA. Enzymes from H. pylori, L. johnsonii,and H. somni are highlighted in cyan. The E. coli, H. pylori, and L. johnsonii MccB were found to be mutually orthogonal enzymes. (C) The E. coli, H. pylori, and L. johnsonii enzymes catalyze C-terminal thioesterification of their respective MccA-N7G sequences and are orthogonal to one another. (D) LC-MS analysis of GFP-EcTeCH, GFP-HpTeCH, and GFP-LjTeCH shows that MccA-N7Gs from E. coli, H. pylori, and L. johnsonii can be deployed as TeCH-tags for C-terminal protein modification. (E) MccBs from E. coli, H. pylori, and L. johnsonii modify only proteins tagged with their cognate TeCH-tags. (F) In a mixture of GFPs fused to TeCH-tags from E. coli, H. pylori, and L. johnsonii, the MccB homologs from E. coli, H. pylori, and L. johnsonii selectively modify their cognate TeCH-tags.