Membrane Anchoring and Ion-Entry Dynamics in P-type ATPase Copper Transport

Abstract

Cu þ -specific P-type ATPase membrane protein transporters regulate cellular copper levels. The lack of crystal structures in Cu þ -binding states has limited our understanding of how ion entry and binding are achieved. Here, we characterize the molecular basis of Cu þ entry using molecular-dynamics simulations, structural modeling, and in vitro and in vivo functional assays. Protein structural rearrangements resulting in the exposure of positive charges to bulk solvent rather than to lipid phosphates indicate a direct molecular role of the putative docking platform in Cu þ delivery. Mutational analyses and simulations in the presence and absence of Cu þ predict that the ion-entry path involves two ion-binding sites: one transient Met148-Cys382 site and one intramembranous site formed by trigonal coordination to Cys384, Asn689, and Met717. The results reconcile earlier biochemical and x-ray absorption data and provide a molecular understanding of ion entry in Cu þ -transporting P-type ATPases.

<p>Pump Proton and Laryngeal H⁺/K⁺ ATPases</p>

“…9 As a byproduct of the pump activity, a pH gradient forms on either side of the membrane. Four types of proton pumps with ATPase activity have been recognized: P-type, [10][11][12][13][14] F-type, [15][16][17] V-type, [18][19][20] and ABC ATPases. 18…”

Main Molecular Pathways Associated with Copper Tolerance Response in Imperata cylindrica by de novo Transcriptome Assembly

“…Genes encoding for Hephaestin-like protein and ABC transporter C family member 8 were part of this group. Hephaestin-like protein may function as a ferroxidase and may be involved in Cu transport and homeostasis; moreover, ABC transporter belongs to a large protein family that in plants are involved in the transport of a range of essential and PTEs (as Cu +2 , Zn +2 , Cd +2 , Pb +2 ) across cell membranes [ 7 , 34 , 49 ]. The Probable copper-transporting ATPase HMA5, in turn, plays a key role in transmembrane Cu transport and is specifically induced by Cu in plants [ 50 ].…”

Tracking Membrane Protein Dynamics in Real Time

“…Due to the lack of crystal structures trapped in ion-binding states, how heavy-metal ions enter and bind to the internal transport sites remain unknown. A combined modeling-simulation approach predicted membrane partitioning of a protein-associated platform for ion-delivering chaperones and a putative ion-entry mechanism in Cu + -transporting (CopA) P-type ATPases (Gronberg et al 2016 ). Hence, atomistic MD simulations can clearly provide critical insight into dynamical processes in membrane proteins that are difficult to assess with experimental methods, but the method is limited by the time scales that can be sampled, which frequently correspond only to a fraction of the full reaction.…”