Journal
SCIENCE
Volume 318, Issue 5852, Pages 970-974Publisher
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1148790
Keywords
-
Categories
Funding
- NIDDK NIH HHS [DK42303] Funding Source: Medline
- NIGMS NIH HHS [GM076477] Funding Source: Medline
Ask authors/readers for more resources
An unexpected biochemical strategy for chain initiation is described for the loading module of the polyketide synthase of curacin A, an anticancer lead derived from the marine cyanobacterium Lyngbya majuscula. A central GCN5-related N-acetyltransferase (GNAT) domain bears bifunctional decarboxylase/S-acetyltransferase activity, both unprecedented for the GNAT superfamily. A CurA loading tridomain, consisting of an adaptor domain, the GNAT domain, and an acyl carrier protein, was assessed biochemically, revealing that a domain showing homology to GNAT (GNAT(L)) catalyzes (i) decarboxylation of malonyl-coenzyme A (malonyl-CoA) to acetyl-CoA and (ii) direct S-acetyl transfer from acetyl-CoA to load an adjacent acyl carrier protein domain (ACP(L)). Moreover, the N-terminal adapter domain was shown to facilitate acetyl- group transfer. Crystal structures of GNAT(L) were solved at 1.95 angstroms (ligand-free form) and 2.75 angstroms (acyl-CoA complex), showing distinct substrate tunnels for acyl-CoA and holo-ACP(L) binding. Modeling and site-directed mutagenesis experiments demonstrated that histidine-389 and threonine-355, at the convergence of the CoA and ACP tunnels, participate in malonyl-CoA decarboxylation but not in acetyl-group transfer. Decarboxylation precedes acetyl- group transfer, leading to acetyl-ACP(L) as the key curacin A starter unit.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available