Two new T-state crystal structures of maize C 4 -phosphoenolpyruvate carboxylase reveal and suggest novel structural features of the allosteric regulation and carboxylation step.

Autor: Carrizosa-Carbajal EI; Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México, Mexico., González-Segura L; Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México, Mexico. Electronic address: liliang@unam.mx., Muñoz-Clares RA; Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México, Mexico. Electronic address: clares@unam.mx.
Jazyk: angličtina
Zdroj: International journal of biological macromolecules [Int J Biol Macromol] 2024 Nov; Vol. 279 (Pt 2), pp. 135134. Date of Electronic Publication: 2024 Aug 28.
DOI: 10.1016/j.ijbiomac.2024.135134
Abstrakt: To get a deeper understanding of the structural bases of the allosteric transition between T and R states of plant and bacterial phosphoenolpyruvate carboxylases (PEPCs), we obtained the first T-state crystal structures of the maize photosynthetic PEPC (ZmPEPC-C 4 ) and exhaustively compared them with the previously reported R-state ZmPEPC-C 4 and other T-state structures. We identified previously unrecognized significant conformational changes in the T state: that of the α8-α9 loop, which connects the two kinds of activator allosteric sites with the active site, the conversion of the α30 helix into a 3 10 helix, leading to the disorganization of the active site lid and activators allosteric sites, and the closure of the inhibitor allosteric-site lid. Additionally, we identified previously overlooked, highly conserved residues of potential interest in the allosteric transition, including two histidines whose protonation might stabilize the T state. The crystal structures reported here also suggest similar tetrameric quaternary arrangements of PEPC enzymes in the R and T states, and the location of the bicarbonate binding site, as well as the conformational changes required for the carboxylation step. Our findings and working hypothesis advance the understanding of the structural features of the allosteric PEPC enzymes and provide a foundation for future experiments.
Competing Interests: Declaration of competing interest The authors declare no conflict of interes.
(Copyright © 2024. Published by Elsevier B.V.)
Databáze: MEDLINE
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