The high structural homology in the auxiliary cluster binding region between BtrN, fellow AdoMet radical dehydrogenase anSME, and molybdenum cofactor biosynthetic enzyme MoaA provides support for the establishment of an AdoMet radical structural motif that is likely common to all the AdoMet radical enzymes in this subgroup. Most appear to be involved in prosthetic group cofactor and peptide maturation processes.
Puehringer S, Metlitzky M, Schwarzenbacher R
The pyrroloquinoline quinone biosynthesis pathway revisited: a structural approach
▸ Abstract
BACKGROUND: The biosynthesis pathway of Pyrroloquinoline quinone, a bacterial redox active cofactor for numerous alcohol and aldose dehydrogenases, is largely unknown, but it is proven that at least six genes in Klebsiella pneumoniae (PqqA-F) are required, all of which are located in the PQQ-operon.
RESULTS: New structural data of some PQQ biosynthesis proteins and their homologues provide new insights and functional assignments of the proteins in the pathway. Based on sequence analysis and homology models we propose the role and catalytic function for each enzyme involved in this intriguing biosynthesis pathway.
CONCLUSION: PQQ is derived from the two amino acids glutamate and tyrosine encoded in the precursor peptide PqqA. Five reactions are necessary to form this quinone cofactor. The PqqA peptide is recognised by PqqE, which links the C9 and C9a, afterwards it is accepted by PqqF which cuts out the linked amino acids. The next reaction (Schiff base) is spontaneous, the following dioxygenation is catalysed by an unknown enzyme. The last cyclization and oxidation steps are catalysed by PqqC. Taken together the known facts of the different proteins we assign a putative function to all six proteins in PQQ biosynthesis pathway.
X-ray analysis of butirosin biosynthetic enzyme BtrN redefines structural motifs for AdoMet radical chemistry
▸ Abstract
The 2-deoxy-scyllo-inosamine (DOIA) dehydrogenases are key enzymes in the biosynthesis of 2-deoxystreptamine-containing aminoglycoside antibiotics. In contrast to most DOIA dehydrogenases, which are NAD-dependent, the DOIA dehydrogenase from Bacillus circulans (BtrN) is an S-adenosyl-l-methionine (AdoMet) radical enzyme. To examine how BtrN employs AdoMet radical chemistry, we have determined its structure with AdoMet and substrate to 1.56 Å resolution. We find a previously undescribed modification to the core AdoMet radical fold: instead of the canonical (β/α)6 architecture, BtrN displays a (β5/α4) motif. We further find that an auxiliary [4Fe-4S] cluster in BtrN, thought to bind substrate, is instead implicated in substrate-radical oxidation. High structural homology in the auxiliary cluster binding region between BtrN, fellow AdoMet radical dehydrogenase anSME, and molybdenum cofactor biosynthetic enzyme MoaA provides support for the establishment of an AdoMet radical structural motif that is likely common to ∼6,400 uncharacterized AdoMet radical enzymes.
Proc Natl Acad Sci U S A
2013;110(40):15949-15954
| PubMed ID:
24048029
Grell TA, Goldman PJ, Drennan CL
SPASM and Twitch Domains in AdoMet Radical Enzyme Structures
▸ Abstract
S-adenosylmethionine (AdoMet) radical enzymes use S-adenosylmethionine AdoMet and a [4Fe-4S] cluster to catalyze a diverse array of reactions. They adopt a partial TIM barrel fold with N- and C-terminal extensions that tailor the structure of the enzyme to its specific function. One extension, termed a SPASM domain, binds two auxiliary [4Fe-4S] clusters and is present within peptide-modifying enzymes. The first structure of a SPASM-containing enzyme, anaerobic sulfatase maturating enyzme, revealed unexpected similarities to two non-SPASM proteins, butirosin biosynthetic enzyme BtrN and molybdenum cofactor biosynthetic enzyme MoaA. The latter two enzymes bind one auxiliary cluster and exhibit a partial SPASM motif, coined a Twitch domain. Here we review the function, structure, and role of auxiliary cluster domains within the AdoMet radical enzyme superfamily.
