3D electron microscopy reveals the variable deposition and protein dynamics of the peripheral pyruvate dehydrogenase component about the core
Year: 2003
Type: article
Abstract: Cryo-electron microscopy was exploited to reveal and study the influence of pyruvate dehydrogenase (E1) occupancy on the conformational states of the Saccharomyces cerevisiae pyruvate dehydrogenase complex (PDC). Structures representative of PDC preparations with approximately 40% and full E1 occupancy were determined after the electron microscopy images from each preparation were classified according to their sizes. The reconstructions derived from two size groups showed that the deposition of the E1 molecules associated with the larger complex is, unexpectedly, not icosahedrally arranged, whereas in the smaller complex the E1 molecules have an arrangement and architecture similar to their more ordered deposition in the WT bovine kidney PDC. This study also shows that the linker of dihydrolipamide acetyltransferase (E2) that tethers E1 to the E2 core increases in length from approximately 50 to 75 A, accounting largely for the size difference of the smaller and larger structures, respectively. Extensive E1 occupancy of its 60 E2 binding sites favors the extended conformation of the linker associated with the larger complex and appears to be related to the loss of icosahedral symmetry of the E1 molecules. However, the presence of a significant fraction of larger molecules also in the WT PDC preparation with low E1 occupancy indicates that the conformational variability of the linker contributes to the overall protein dynamics of the PDC and the variable deposition of E1. The flexibility of the complex may enhance the catalytic proficiency of this macromolecular machine by promoting the channeling of the intermediates of catalysis between the active sites.
Institution: The University of Texas at Austin
Language: English
Subfield: Biochemistry
Domain: Life Sciences
Open Access status: green
Awards: G1016616661, BIOCHEMISTRY OF ALPHA-KETO ACID DEHYDROGENASE COMPLEXES, G3081792669, G3288381071, Structure and Assembly of KSHV Capsids and Virions, G5189506458, STRUCTURAL STUDIES OF HUMAN CYTOMEGALOVIRUS, G825083238, 3D ELECTRON MICROSCOPY OF PYRUVATE DEHYDROGENASE, 3D ELECTRON MICROSCOPY OF PYRUVATE DEHYDROGENASE
OpenAlex ID: W2092188649