Dephosphorylation and ion binding in prokaryotic calcium transport

Abstract

Calcium (Ca 2+ ) signaling is fundamental to cellular processes in both eukaryotic and prokaryotic organisms. While the mechanisms underlying eukaryotic Ca 2+ transport are well documented, an understanding of prokaryotic transport remains nascent. LMCA1, a Ca 2+ adenosine triphosphatase (ATPase) from Listeria monocytogenes , has emerged as a prototype for elucidating structure and dynamics in prokaryotic Ca 2+ transport. Here, we used a multidisciplinary approach integrating kinetics, structure, and dynamics to unravel the intricacies of LMCA1 function. A cryo–electron microscopy (cryo-EM) structure of a Ca 2+ -bound E1 state showed ion coordination by Asp 720 , Asn 716 , and Glu 292 . Time-resolved x-ray solution scattering experiments identified phosphorylation as the rate-determining step. A cryo-EM E2P state structure exhibited remarkable similarities to a SERCA1a E2-P* state, which highlights the essential role of the unique P-A domain interface in enhancing dephosphorylation rates and reconciles earlier proposed mechanisms. Our study underscores the distinctiveness between eukaryotic and prokaryotic Ca 2+ ATPase transport systems and positions LMCA1 as a promising drug target for developing antimicrobial strategies.