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In this review the molecular characteristics and reaction mechanisms of different Ca2+ transport systems associated with various membranes in muscle cells will be summarized. The following topics will be discussed in detail: a brief history of early observations concerning maintenance and regulation of cellular Ca2+ homeostasis, characterization of the Ca2+ pumps residing in plasma membranes and sarco(endo)plasmic reticulum, mitochondrial Ca2+ transport, Ca2+ -binding proteins, coordinated expression of Ca2+ transport systems, a general background of muscle excitation-contraction coupling with emphasis to the calcium release channels of plasma membrane and sarcoplasmic reticulum, the structure and function of dihydropyridine and ryanodine receptors of skeletal and cardiac muscles, and finally their disposition in various types of muscles.
In this article the morphology of sarcoplasmic reticulum, classification of Ca2+ -ATPase (SERCA) isoenzymes presented in this membrane system, as well as their topology will be reviewed. The focus is on the structure and interactions of Ca2+ -ATPase determined by electron and X-ray crystallog2r+aphy, lamellar X-ray and neutron diffraction analysis of the profile structure of Ca2+ -ATPase in sarcoplasmic reticulum multilayers. In addition, targeting of the Ca2+ -ATPase to the sarcoplasmic reticulum is discussed.
Numerous results on membrane lipid composition from different regions of autopsied Alzheimer's disease brains in comparison with corresponding fractions isolated from control brains revealed significant differences in serine- and ethanolamine-containing glycerophospholipid as well as in glycosphingolipid content. Changes in membrane lipid composition are frequently accompanied by alterations in membrane fluidity, hydrophobic mismatch, lipid signaling pathways, transient formation and disappearance of lipid microdomains, changes in membrane permeability to cations and variations of other membrane properties. In this review we focus on possible implications of altered membrane composition on b-amyloid precursor protein (APP) and on proteolysis of APP leading eventually to the formation of neurotoxic b-amyloid (Ab) peptides, the major proteinaceous component of extracellular senile plaques, directly involved in Alzheimer's disease pathogenesis.
The paradigm of annexins as phospholipid-binding proteins interacting with membranes in a calcium-dependent manner has been recently questioned in light of observations that some annexin isoforms may behave like membrane integral proteins or remain associated with their target membranes at low, resting, concentrations of Ca2+ in the cytoplasm. In addition, an evidence has been presented that some annexins (annexins I, VI and VII) bind in vitro ATP and GTP, and upon binding the nucleotide the in vitro activity of these proteins is modified. However, annexins do not contain Walker A and B consensus sequences for ATP/GTP binding. This review presents the hypothesis that a new ATP-binding motif exists within the annexin molecules and that ATP may play a role of functional ligand for annexins also in vivo
1,12-Dodecanedioic acid, the end-product of w-hydroxylation of lauric acid, stimulates in a concentration dependent manner, phosphatidylethanolamine synthesis via ethanolamine-specific phospholipid base exchange reaction in rat liver endoplasmic reticulum. On the other hand, administration to rats of 10-undecynoic acid, a specific inhibitor of w-hydroxylation reaction catalyzed by cytochrome P450 4A1, inhibits the ethanolamine-specific phospholipid base exchange activity by 30%. This is accompanied by a small but significant decrease in phosphatidylethanolamine content in the endoplasmic reticulum and inhibition of cytochrome P450 4A1. On the basis of these results it can be proposed that a functional relationship between cytochrome P450 4A1 and phosphatidylethanolamine synthesis exists in rat liver. Cytochrome P450 4A1 modulates the cellular level of lauric acid, an inhibitor of phospholipid synthesis. In turn, ethanolamine-specific phospholipid base exchange reaction provides molecular species of phospholipids, containing mainly long-chain polyunsaturated fatty acid moieties, required for the optimal activity of cytochrome P450 4A1.
The purpose of this article is to provide a concise overview of the characterization of auxotrophic mutated cells to the precursors of lipid synthesis, and of the identification of specific genes encoding enzymatic proteins involved in this process. The focus is on enzymes catalyzing the synthesis of phosphatidylserine and phosphatidylethanolamine in Saccharomyces cerevisiae and Chinese hamster ovary cells, two cell types frequently used by investigators studying the mechanisms of genetic control of metabolic processes.
The purpose of this article is to provide a concise overview of the characterization of auxotrophic mutated cells to the precursors of lipid synthesis, and of the identification of specific genes encoding enzymatic proteins involved in this process. The focus is on enzymes catalyzing the synthesis of phosphatidylserine and phosphatidylethanolamine in Saccharomyces cerevisiae and Chinese hamster ovary cells, two cell types frequently used by investigators studying the mechanisms of genetic control of metabolic processes.
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