7xp7

Publication Abstract from PubMed

The recruitment of trans-acting enzymes by nonribosomal peptide synthetase (NRPS) assembly line is rarely reported. ColB1 is a flavin-dependent dehydrogenase that is recruited by an NRPS terminal condensation domain (Ct domain) and catalyzes peptidyl carrier protein (PCP)-tethered cysteine dehydrogenation in collismycin biosynthesis. We here report the crystal structure of ColB1 complexed with FAD and reveal a typical structural fold of acyl-CoA dehydrogenases (ACADs). However, ColB1 shows distinct structural features from ACADs in substrate recognition both at the entrance of and inside the active site. Site-directed mutagenesis and substrate modeling establish a Glu393-mediated catalytic mechanism, by which the cysteine substrate is sandwiched between Glu393 and FAD to facilitate C(alpha) proton abstraction and C(beta) hydride migration. A ColB1-PCP-Ct complex model is generated, providing structural basis for the unique recruitment interactions between ColB1 and the associated NRPS. These results add insights into the mechanisms by which trans-acting enzymes function in an assembly line.

Structure-Based Mechanistic Insights into ColB1, a Flavoprotein Functioning in-trans in the 2,2'-Bipyridine Assembly Line for Cysteine Dehydrogenation.,Ma X, Tang Z, Ding W, Liu T, Yang D, Liu W, Ma M ACS Chem Biol. 2023 Jan 20;18(1):18-24. doi: 10.1021/acschembio.2c00785. Epub , 2023 Jan 5. PMID:36603145^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.