| Autor: |
Yingqi Gu, Hong Zhou, Z., McCarthy, Diane B., Reed, Lester J., Stoops, James K. |
| Předmět: |
|
| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; 6/10/2003, Vol. 100 Issue 12, p7015, 6p, 1 Black and White Photograph, 5 Diagrams |
| Abstrakt: |
Cryo-electron microscopy was exploited to reveal and study the influence of pyruvate dehydrogenase (E[sub 1]) occupancy on the conformational states of the Saccharomyces cerevisiae pyruvate dehydrogenase complex (PDC). Structures representative of PDC preparations with ≈40% and full E[sub 1] 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 E[sub 1] molecules associated with the larger complex is, unexpectedly, not icosahedrally arranged, whereas in the smaller complex the E[sub 1] 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 (E[sub 2]) that tethers E[sub 1] to the E[sub 2] core increases in length from ≈50 to 75 Å, accounting largely for the size difference of the smaller and larger structures, respectively. Extensive E[sub 1] occupancy of its 60 E[sub 2] 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 E[sub 1] molecules. However, the presence of a significant fraction of larger molecules also in the WT PDC preparation with low E[sub 1] occupancy indicates that the conformational variability of the linker contributes to the overall protein dynamics of the PDC and the variable deposition of E[sub 1]. 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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
