Electrostatic interactions between single arginine and phospholipids modulate physiological properties of sarcoplasmic reticulum Ca-ATPase.

Arg324 of sarcoplasmic reticulum Ca-ATPase forms electrostatic interactions with the phosphate moiety of phospholipids in most reaction states, and a hydrogen bond with Tyr122 in other states. Using site-directed mutagenesis, we explored the functional roles of Arg324 interactions, especially those with lipids, which at first glance might seem too weak to modulate the function of such a large membrane protein. The hydrogen bond forms transiently and facilitates Ca binding from the cytoplasmic side.

Angle change of the A-domain in a single SERCA1a molecule detected by defocused orientation imaging.

The sarcoendoplasmic reticulum Ca-ATPase (SERCA) transports Ca ions across the membrane coupled with ATP hydrolysis. Crystal structures of ligand-stabilized molecules indicate that the movement of actuator (A) domain plays a crucial role in Ca translocation. However, the actual structural movements during the transitions between intermediates remain uncertain, in particular, the structure of E2PCa has not been solved.

Nanodisc-based kinetic assays reveal distinct effects of phospholipid headgroups on the phosphoenzyme transition of sarcoplasmic reticulum Ca-ATPase.

Sarco(endo)plasmic reticulum Ca-ATPase catalyzes ATP-driven Ca transport from the cytoplasm to the lumen and is critical for a range of cell functions, including muscle relaxation. Here, we investigated the effects of the headgroups of the 1-palmitoyl-2-oleoyl glycerophospholipids phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylglycerol (PG) on sarcoplasmic reticulum (SR) Ca-ATPase embedded into a nanodisc, a lipid-bilayer construct harboring the specific lipid. We found that Ca-ATPase activity in a PC bilayer is comparable with that of SR vesicles and is suppressed in the other phospholipids, especially in PS.

Membrane Perturbation of ADP-insensitive Phosphoenzyme of Ca-ATPase Modifies Gathering of Transmembrane Helix M2 with Cytoplasmic Domains and Luminal Gating.

Ca transport by sarcoplasmic reticulum Ca-ATPase involves ATP-dependent phosphorylation of a catalytic aspartic acid residue. The key process, luminal Ca release occurs upon phosphoenzyme isomerization, abbreviated as E1PCa (reactive to ADP regenerating ATP and with two occluded Ca at transport sites) → E2P (insensitive to ADP and after Ca release). The isomerization involves gathering of cytoplasmic actuator and phosphorylation domains with second transmembrane helix (M2), and is epitomized by protection of a Leu-proteinase K (prtK) cleavage site on M2.

[EEG Beta and Gamma Powers When Comparing Certain Psychophysiological States with Normal and Weakened Electromyogram of Facial Muscles.].

The aim of the present study was to investigate EMG contamination on high-frequency scalp electroencephalogram (EEG) during comparisons of certain cognitive tasks performance. 19 healthy women who performed similar test tasks before and after cosmetic injections of Dysport in various face regions for reduction of facial muscles activity took part in the study. The test tasks were focused on induction of emotional states with different valences, on memory storing and extraction of verbal information.