Amino acid sequences of pyridoxal 5'-phosphate binding sites and fluorescence resonance energy transfer in chicken liver fatty acid synthase

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Abstract
The amino aciod sequences associated with pyridoxal 5''-phosphate binding sites in chicken liver fatty acid synthase have been determined: a site whose modification causes selective inhibition of the enoyl reductase activity and a site (site I) that is not associated with enzymatic activity. The amino acid sequences of peptides obtained by trypsin hydrolysis of the pyridoxamine 5''-phosphate labeled enzyme were determined. For the site associated with enoyl reductase activity, the sequence similarities between chicken and goose are extensive and include the sequence Ser-X-X-Lys, a characteristic structural feature of pyridoxamine enzymes. In addition, the spatial relationships between the pyridoxal 5''-phosphate binding sites and reductase site(s) have been studied with fluorescence resonance energy-transfer techniques. The distances between site I and the enoyl reductase and .beta.-ketoacyl reductase sites are > 50 and 41-44 .ANG., respectively. The distance between the two reductase sites is > 49 .ANG.