3skv

Publication Abstract from PubMed

SsfX3 is a GDSL family acyltransferase that transfers salicylate to the C4 hydroxyl of a tetracycline intermediate in the penultimate step during biosynthesis of the anticancer natural product SF2575. The C4 salicylate takes the place of the more common C4 dimethylamine functionality, making SsfX3 the first acyltransferase identified to act on a tetracycline substrate. The crystal structure of SsfX3 was determined at 2.5 A, revealing two distinct domains: an N-terminal beta-sandwich domain that resembles a carbohydrate binding module (CBM) and a C-terminal catalytic domain that contains the atypical alpha/beta-hydrolase fold found in the GDSL hydrolase family of enzymes. The active site lies at one end of a large open binding pocket, which is spatially defined by structural elements from both the N-terminal and C-terminal domains. Mutational analysis in the putative substrate binding pocket identified residues from both domains that are important for binding the acyl donor and acceptor. Furthermore, removal of the N-terminal CBM-like domain rendered the stand-alone alpha/beta hydrolase domain inactive. The additional, noncatalytic module is therefore proposed to be required to define the binding pocket and provide sufficient interactions with the spatially extended, tetracyclic substrate. SsfX3 was also demonstrated to accept a variety of nonnative acyl groups. This relaxed substrate specificity toward the acyl donor allowed the chemoenzymatic biosynthesis of C4-modified analogs of the immediate precursor to the bioactive SF2575; these were used to assay the structure activity relationships at the C4 position.

Structural and biochemical characterizations of the salicylyl-acyltranferase SSFX3 from a tetracycline biosynthetic pathway.,Pickens LB, Sawaya MR, Rasool H, Pashkov I, Yeates TO, Tang Y J Biol Chem. 2011 Sep 29. PMID:21965680^[1]

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