Dephosphorylation and ion binding in prokaryotic calcium transport

Calcium (Ca²⁺) signaling is fundamental to cellular processes in both eukaryotic and prokaryotic organisms. While the mechanisms underlying eukaryotic Ca²⁺ transport are well documented, an understanding of prokaryotic transport remains nascent. LMCA1, a Ca²⁺ adenosine triphosphatase (ATPase) from Listeria monocytogenes, has emerged as a prototype for elucidating structure and dynamics in prokaryotic Ca²⁺ 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 Ca²⁺-bound E1 state showed ion coordination by Asp⁷²⁰, Asn⁷¹⁶, and Glu²⁹². 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 Ca²⁺ ATPase transport systems and positions LMCA1 as a promising drug target for developing antimicrobial strategies.