7mgv

Publication Abstract from PubMed

Among the ribosomally synthesized and post-translationally modified peptide (RiPP) natural products, "graspetides" (formerly known as microviridins) contain macrocyclic esters and amides that are formed by ATP-grasp ligase tailoring enzymes using the side chains of Asp/Glu as acceptors and Thr/Ser/Lys as donors. Graspetides exhibit diverse patterns of macrocylization and connectivities exemplified by microviridins, that have a caged tricyclic core, and thuringin and plesiocin that feature a "hairpin topology" with cross-strand omega-ester bonds. Here, we characterize chryseoviridin, a new type of multicore RiPP encoded by Chryseobacterium gregarium DS19109 (Phylum Bacteroidetes) and solve a 2.44 A resolution crystal structure of a quaternary complex consisting of the ATP-grasp ligase CdnC bound to ADP, a conserved leader peptide and a peptide substrate. HRMS/MS analyses show that chryseoviridin contains four consecutive five- or six-residue macrocycles ending with a microviridin-like core. The crystal structure captures respective subunits of the CdnC homodimer in the apo or substrate-bound state revealing a large conformational change in the B-domain upon substrate binding. A docked model of ATP places the gamma-phosphate group within 2.8 A of the Asp acceptor residue. The orientation of the bound substrate is consistent with a model in which macrocyclization occurs in the N- to C-terminal direction for core peptides containing multiple Thr/Ser-to-Asp macrocycles. Using systematically varied sequences, we validate this model and identify two- or three-amino acid templating elements that flank the macrolactone and are required for enzyme activity in vitro. This work reveals the structural basis for omega-ester bond formation in RiPP biosynthesis.

Structural Basis for a Dual Function ATP Grasp Ligase That Installs Single and Bicyclic omega-Ester Macrocycles in a New Multicore RiPP Natural Product.,Zhao G, Kosek D, Liu HB, Ohlemacher SI, Blackburne B, Nikolskaya A, Makarova KS, Sun J, Barry Iii CE, Koonin EV, Dyda F, Bewley CA J Am Chem Soc. 2021 Jun 2;143(21):8056-8068. doi: 10.1021/jacs.1c02316. Epub 2021 , May 24. PMID:34028251^[1]

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