ausblenden:
Schlagwörter:
EXCHANGE-MASS-SPECTROMETRY; RIBULOSE 1,5-BISPHOSPHATE CARBOXYLASE;
HYDROGEN-EXCHANGE; ELECTRON-MICROSCOPY; STRUCTURE ELUCIDATION;
INTERACTION NETWORKS; CROSS-LINKING; VISUALIZATION; INTERMEDIATE;
BISPHOSPHATEBiochemistry & Molecular Biology; Cell Biology;
Zusammenfassung:
How AAA(+) chaperones conformationally remodel specific target proteins in an ATP-dependent manner is not well understood. Here, we investigated the mechanism of the AAA(+) protein Rubisco activase (Rca) in metabolic repair of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits containing eight catalytic sites. Rubisco is prone to inhibition by tight-binding sugar phosphates, whose removal is catalyzed by Rca. We engineered a stable Rca hexamer ring and analyzed its functional interaction with Rubisco. Hydrogen/deuterium exchange and chemical crosslinking showed that Rca structurally destabilizes elements of the Rubisco active site with remarkable selectivity. Cryo-electron microscopy revealed that Rca docks onto Rubisco over one active site at a time, positioning the C-terminal strand of RbcL, which stabilizes the catalytic center, for access to the Rca hexamer pore. The pulling force of Rca is fine-tuned to avoid global destabilization and allow for precise enzyme repair.
