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.
Gipson
Preeti
P
Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt, Germany.
Mills
Deryck J
DJ
Wouts
Remco
R
Grininger
Martin
M
Vonck
Janet
J
Kühlbrandt
Werner
W
D000213:Acyl Carrier Protein / Q000737:chemistry* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods; D064429:Fatty Acid Synthases / Q000737:chemistry* / Q000648:ultrastructure; D008958:Models, Molecular; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000648:ultrastructure
D000213:Acyl Carrier Protein; D029701:Saccharomyces cerevisiae Proteins; D064429:Fatty Acid Synthases