Direct structural insight into the substrate-shuttling mechanism of yeast fatty acid synthase by electron cryomicroscopy.

Yeast fatty acid synthase (FAS) is a 2.6-MDa barrel-shaped multienzyme complex, which carries out cyclic synthesis of fatty acids. By electron cryomicroscopy of single particles we obtained a three-dimensional map of yeast FAS at 5.9-A resolution. Compared to the crystal structures of fungal FAS, the EM map reveals major differences ...
and new features that indicate a considerably different arrangement of the complex in solution compared to the crystal structures, as well as a high degree of variance inside the barrel. Distinct density regions in the reaction chambers next to each of the catalytic domains fitted the substrate-binding acyl carrier protein (ACP) domain. In each case, this resulted in the expected distance of approximately 18 A from the ACP substrate-binding site to the active site of the catalytic domains. The multiple, partially occupied positions of the ACP within the reaction chamber provide direct structural insight into the substrate-shuttling mechanism of fatty acid synthesis in this large cellular machine.
Mesh Terms:
Acyl Carrier Protein, Cryoelectron Microscopy, Fatty Acid Synthases, Models, Molecular, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Proc Natl Acad Sci U S A
Date: May. 18, 2010
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