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.
Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Michele
M
Gunsior
Steven D
SD
Breazeale
Amanda J
AJ
Lind
Jacques
J
Ravel
James W
JW
Janc
Craig A
CA
Townsend
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