Structure and molecular organization of mammalian fatty acid synthase.

De novo synthesis of fatty acids in the cytosol of animal cells is carried out by the multifunctional, homodimeric fatty acid synthase (FAS). Cryo-EM analysis of single FAS particles imaged under conditions that limit conformational variability, combined with gold labeling of the N termini and structural analysis of the FAS monomers, reveals two coiled monomers in an overlapping arrangement. Comparison of dimeric FAS structures related to different steps in the fatty acid synthesis process indicates that only limited local rearrangements are required for catalytic interaction among different functional domains.