Divalent cation and lipid-protein interactions of biomembranes

1993 ◽  
Vol 13 (3) ◽  
pp. 143-157 ◽  
Author(s):  
F. Y. Yang ◽  
Y. G. Huang ◽  
Y. P. Tu
Keyword(s):  
Adenylate Cyclase ◽  
Atpase Activity ◽  
Enzymatic Activity ◽  
Divalent Cation ◽  
Protein Interactions ◽  
Physical State ◽  
Divalent Cations ◽  
Activity Change ◽  
Lipid Protein Interactions

Divalent cations play an important role in the functions of biomembranes. This review deals with three topics: (1) Mg2+-mediated change in physical state of phospholipid induces conformation and activity change of reconstituted mitochondrial H+-ATPase, (2) a proper transmembrane Ca2+ gradient is essential for the higher enzymatic activity of adenylate cyclase, and (3) role of transmembrane Ca2+ gradient in the modulation of reconstituted sarcoplasmic reticulm Ca2+-ATPase activity.

Extracellular Calcium And Platelets

1981 ◽  
Author(s):  
P M Taylor ◽  
S Heptinstall
Keyword(s):  
Divalent Cation ◽  
Binding Sites ◽  
Divalent Cations ◽  
Extracellular Calcium ◽  
Time Dependent ◽  
Aggregation Process ◽  
Platelet Surface ◽  
Intracellular Pool ◽  
Continuous Movement

To gain more information on the role of extracellular Ca in platelet behaviour, the movement of 45Ca between plasma and platelets has been studied. Ttoo experimental procedures have been used: platelets were either studied in plasma that contained near-physiological levels of divalent cations or were studied in divalent cation-depleted plasma.There was a continuous movement of Ca from plasma into platelets when the latter were suspended in plasma that contained near-physiological levels of divalent cations. The iptake was linear with time (2.0 to 2.5 ng ion Ca/109 platelets/60 mins) and was faster at 37°C than at 25°C. The amount of Ca taken up by the platelets increased as the extracellular Ca level was increased and was markedly inhibited by Mg. Sr did not affect the uptake. EGTA displaced only a small amount of the Ca that associated with the plater lets which indicated that Ca was taken up into an intracellular pool rather than sinply bound to the platelet surface. The relevance of this movement of Ca into the cells to platelet behaviour has not been established.Studies using platelets suspended in divalent cation- depleted plasma shewed that extracellular Ca was in equilibrium with Ca bound at or near the platelet surface. The binding of Ca was time-dependent but saturable (0.30 to 0.50 ng ion Ca/109 platelets/30 mins), and the majority was readily displaced by EGTA. The amount of Ca bound to the cells increased as the extracellular Ca level was increased but was little affected by an excess of either Mg or Sr. Mare Ca bound to platelets when they were incubated at 25°C than at 37°C. This was because platelets lost their ability to bind Ca when they were incubated at 37°C in divalent cation-depleted plasma. This phenomenon was time-dependent and irreversible and was paralleled by a loss in the ability of the platelets to aggregate. These Ca binding sites would seem to be relevant to the aggregation process.

scholarly journals Assessing the Role of Lipids in the Molecular Mechanism of Membrane Proteins

2021 ◽  
Vol 22 (14) ◽  
pp. 7267
Author(s):  
Léni Jodaitis ◽  
Thomas van Oene ◽  
Chloé Martens
Keyword(s):  
Membrane Proteins ◽  
Molecular Mechanism ◽  
Protein Interactions ◽  
Protein Function ◽  
Biological Membrane ◽  
Allosteric Coupling ◽  
Lipid Protein Interactions ◽  
Experimental Challenge ◽  
Membrane Protein Function

Membrane proteins have evolved to work optimally within the complex environment of the biological membrane. Consequently, interactions with surrounding lipids are part of their molecular mechanism. Yet, the identification of lipid–protein interactions and the assessment of their molecular role is an experimental challenge. Recently, biophysical approaches have emerged that are compatible with the study of membrane proteins in an environment closer to the biological membrane. These novel approaches revealed specific mechanisms of regulation of membrane protein function. Lipids have been shown to play a role in oligomerization, conformational transitions or allosteric coupling. In this review, we summarize the recent biophysical approaches, or combination thereof, that allow to decipher the role of lipid–protein interactions in the mechanism of membrane proteins.

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