H-loop Histidine Catalyzes ATP Hydrolysis in the E. coli ABC-Transporter HlyB
Abstract
Adenosine triphosphate (ATP)-binding cassette (ABC) transporters form a family of molecular motor proteins that couple ATP hydrolysis to substrate translocation across cell membranes. Each nucleotide binding domain of ABC-transporters contains a highly conserved H-loop Histidine residue, whose precise mechanistic role to motor functions has remained elusive. By using combined quantum mechanical and molecular mechanical calculations, we showed that the conserved H-loop residue H662 in E. coli HlyB, a bacterial ABC transporter, can act first as a general acid and then as a general base to facilitate proton transfers in ATP hydrolysis. Without the assistance of H662, direct proton transfer from the lytic water to ATP results in a greatly elevated barrier height. Our findings suggest that the essential function of the H-loop residue H662 is to provide a "chemical linchpin" that shuttles protons between reactants through a relay mechanism, thereby catalyzing ATP hydrolysis in HlyB.
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Cite
@article{arxiv.1304.0052,
title = {H-loop Histidine Catalyzes ATP Hydrolysis in the E. coli ABC-Transporter HlyB},
author = {Yan Zhou and Pedro Ojeda-May and Jingzhi Pu},
journal= {arXiv preprint arXiv:1304.0052},
year = {2017}
}