Premium
Structural and functional characterization of the dehydratase domains of the animal cytosolic fatty acid synthase
Author(s) -
Pasta Saloni,
Witkowski Andrzej,
Joshi Anil,
Smith Stuart
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1011.2
Subject(s) - dehydratase , fatty acid synthase , transferase , biochemistry , active site , atp synthase , enzyme , histidine , protein subunit , stereochemistry , dimer , chemistry , acyl carrier protein , biology , biosynthesis , gene , organic chemistry
The objective of the study was to determine the region of the type I animal fatty acid synthase (FAS) multifunctional polypeptide that comprises the dehydratase (DH) domain and to identify residues essential for catalysis. The 4.5 Å electron density map of porcine FAS can accommodate two subunits of type II DH of E. coli (FabA) suggested that this domain may be twice as long as originally anticipated. Expression of FAS constructs of various length revealed that residues 1–809 are required for ketoacyl synthase and malonyl/acetyl transferase activity and 824–1154 for DH activity. Sequence alignment, modeling and mutational studies reveal that animal DHs consist of two pseudosubunits formed by contiguous regions of the same polypeptide, with one active site per pseudodimer, formed by cooperation of histidine 878 on one subunit and aspartate 1032 on the other; glutamine‐1036 is important in positioning the catalytic aspartate. Thus the type I DH resembles its type II counterpart, except that the former has one active site per pseudodimer as opposed to two per dimer in the latter. These studies also assign a role to part of the previously uncharacterized ‘central core’ region of type I FAS and some modular polyketide synthases as contributing to the catalytic region of the DH domain. (Supported by NIH DK16073).