Yeast fatty acid synthetase: Structure—function relationship and nature of the β-ketoacyl synthetase site

摘要: Abstract Yeast fatty acid synthetase consists of two multifunctional proteins, α and β, which are arranged in a complex α6β6. Electron microscopic studies this led to model for the as an ovate structure consisting equatorial plate-like six arches equally distributed on either side. The bifunctional reagent 1,3-dibromo-2-propanone inhibits by reacting rapidly (t½ ≈7 sec) with juxtapositioned active sulfhydryl groups. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis dibromopropanone-inhibited shows that β subunit is intact nearly absent concomitant appearance oligomers estimated molecular weight 0.4-1.2 × 106. These results indicate subunits crosslinked reagent. Because centers dibromopropanone 5 A apart, it concluded closely packed so thiols adjacent within each other. Furthermore, because structures our only components enough satisfy requirement, proposed “plates” therefore “arches.” Assay partial reactions β-ketoacyl reaction but none other reactions, indicating site action condensing reaction. This conclusion was supported finding pretreatment acetyl-CoA or iodoacetamide prevented from interacting at obviated formation oligomer. observations lead us propose cysteine-SH one pantetheine-SH acyl carrier protein moiety subunit. Thus, enzymically center group attached (plate) malonyl arrangement appears be necessary coupling β-carbon occur yield CO2 product.