Comparing crystal structures of Ca²⁺‐ATPase in the presence of different lipids

Abstract

The activity of the sarco/endoplasmic reticulum Ca 2+ -ATPase (SERCA) depends strongly on the lipid composition of the surrounding membrane. Yet, structural information on SERCA-lipid interaction is still relatively scarce, and the influence of different lipids on the enzyme is not well understood. We have analyzed SERCA crystal structures in the presence of four different phosphatidylcholine lipids of different lengths and doublebond compositions, and we find three different binding sites for lipid head groups, which are apparently independent of the acyl moiety of the lipids used. By comparison with other available SERCA structures with bound lipids, we find a total of five recurring sites, two of which are specific to certain conformational states of the enzyme, two others are state-independent, and one is a crucial site for crystal formation. Three of the binding sites overlap with or are in close vicinity to known binding sites for various SERCA-specific inhibitors and regulators, e.g. thapsigargin, sarcolipin/ phospholamban and cyclopiazonic acid. Whereas the transient sites are amenable to a transient, regulatory influence of lipid molecules, the stateindependent sites probably provide a flexible anchoring of the protein in the fluid bilayer.

Stimulation, Inhibition, or Stabilization of Na,K-ATPase Caused by Specific Lipid Interactions at Distinct Sites

“…13 and 17). Interestingly, crystal structures of Ca-ATPase prepared with different lipids also reveal three specific lipid binding sites in the pockets analogous to those proposed here for Na,KATPase (50). Another recent approach for detection of specific lipid binding to membrane proteins utilizes ion mobility mass spectrometry (51,52).…”

On the molecular mechanism of flippase- and scramblase-mediated phospholipid transport

“…Interestingly, residues in SERCA corresponding to some of these residues, i.e. T254, D258, and N550, together with the 'P+4' residue in M4 (Y618 in Dnf1p or F511 in Drs2p), are in proximity of a binding pocket for a phospholipid molecule identified in several E2 structures of SERCA1a [124,125], suggesting that this primordial lipid-binding site in P2-ATPases might have evolved into a site important for phospholipid translocation in P4-ATPases [32]. As those exit gate residues seem to discriminate di-acylated lipids from lysolipids, it seems likely that the ester linkage between the fatty acyl chain and the glycerol backbone is part of the lipid recognition pocket in P4-ATPases.…”

Specific Activation of the Plant P-type Plasma Membrane H+-ATPase by Lysophospholipids Depends on the Autoinhibitory N- and C-terminal Domains

“…Further studies are needed to clarify the interplay between the solubilizing effect of lysophospholipids and their selective activating effect on the PM H ϩ -ATPase in planta. Several binding sites for lipids have been identified in crystal structures of the model P-type ATPase SERCA (35); of these, four do not appear to serve merely as crystal contacts and could represent tightly bound annular lipids. Of special note is the binding site near the calcium entrance pathway modeled as a phosphatidylethanolamine-binding site in the structures.…”

“…PM Ca 2ϩ -ATPases are strongly activated by acidic phospholipids (29) and contain a binding site for acidic phospholipids that interfere with regulation by a calmodulin-binding terminal domain (30 -32). A phospholipid-binding site is apparent in crystal structures of SERCA (33)(34)(35), and it has been suggested that this site is conserved among distantly related P-type ATPases (36). Lysophosphatidylcholine (lyso-PC) is a detergent-like molecule produced from cleavage of phosphatidylcholine by the enzyme phospholipase A 2 and has been proposed to serve as a signaling molecule in plants (37)(38)(39).…”