The biosynthetic gene cluster for a monocyclic beta-lactam antibiotic, nocardicin A.
The monocyclic beta-lactam antibiotic nocardicin A is related structurally and biologically to the bicyclic beta-lactams comprised of penicillins/cephalosporins, clavams, and carbapenems. Biosynthetic gene clusters are known for each of the latter, but not for monocyclic beta-lactams. A previously cloned gene encoding an enzyme specific to the biosynthetic pathway was used to isolate the nocardicin A cluster from Nocardia uniformis. Sequence analysis revealed the presence of 14 open reading frames involved in antibiotic production, resistance, and export. Among these are a two-protein nonribosomal peptide synthetase system, p-hydroxyphenylglycine biosynthetic genes, an S-adenosylmethionine-dependent 3-amino-3-carboxypropyl transferase (Nat), and a cytochrome P450. Gene disruption mutants of Nat, as well as an activation domain of the NRPS system, led to loss of nocardicin A formation. Several enzymes involved in antibiotic biosynthesis were heterologously overproduced, and biochemical characterization confirmed their proposed activities.
Gunsior
Michele
M
Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Breazeale
Steven D
SD
Lind
Amanda J
AJ
Ravel
Jacques
J
Janc
James W
JW
Townsend
Craig A
CA
D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D007769:Lactams / Q000378:metabolism*; D005810:Multigene Family; D009615:Nocardia / Q000235:genetics
D017931:DNA Primers; D007769:Lactams; C027318:nocardicin