- Calcium ATPase
Calcium ATPase is a form of
P-ATPasewhich transfers calciumafter a musclehas contracted. The calcium ATPase are [ [http://www.nlm.nih.gov/cgi/mesh/2007/MB_cgi?mode=&term=Calcium+ATPase nlm.nih.gov] ] :
*Plasma membrane Ca2+ ATPase
Sarcoplasmic reticulumCa2+ ATPase (SERCA)
Plasma membrane Ca2+ ATPase (PMCA)
The plasma membrane Ca2+ ATPase (PMCA) is a
transport proteinin the plasma membraneof cells that serves to remove calcium(Ca2+) from the cell. It is vital for regulating the amount of Ca2+ within cells. [ cite journal | last =Jensen | first =TP | authorlink = | coauthors = Buckby LE; Empson RM| title = Expression of plasma membrane Ca2+ ATPase family members and associated synaptic proteins in acute and cultured organotypic hippocampal slices from rat. | journal =Brain Research. Developmental Brain Research. | volume =152 | issue = 2| pages =129–136 | publisher = | date =2004 | url = | doi = | pmid = 15351500 | accessdate =2007-01-13 ] In fact, the PMCA is involved in removing Ca2+ from all eukaryoticcells.cite journal | last =Strehler | first =EE | authorlink = | coauthors =Zacharias DA | title =Role of alternative splicing in generating isoform diversity among plasma membrane calcium pumps| journal =Physiological Reviews | volume = 81| issue = 1| pages =21–50 | publisher =American Physiological Society | date =2001 | url = http://physrev.physiology.org/cgi/content/full/81/1/21?ijkey=febc5196952b9604d7293e211729df5e16861525 | doi = | pmid =11152753 | accessdate =2007-01-30 ] There is a very large transmembrane electrochemical gradientof Ca2+ driving the entry of the ioninto cells, yet it is very important for cells to maintain low concentrations of Ca2+ for proper cell signalling; thus it is necessary for the cell to employ ion pumps to remove the Ca2+.cite journal | last =Carafoli | first =E | authorlink = | coauthors = | title =Calcium pump of the plasma membrane | journal =Physiological Reviews | volume =71 | issue =1 | pages =129–153 | publisher = | date =1991 | url =http://physrev.physiology.org/cgi/reprint/71/1/129?ijkey=07dce5327b657cc65fb6152751c728391912b332&keytype2=tf_ipsecsha| doi = | pmid =1986387 | accessdate =2007-01-30 ] The PMCA and the sodium calcium exchanger(NCX) are together the main regulators of intracellular Ca2+ concentrations.Since it transports Ca2+ into the extracellular space, the PMCA is also an important regulator of the calcium concentration in the extracellular space. cite journal | last =Talarico Jr | first =EF | authorlink = | coauthors =Kennedy BG; Marfurt CF; Loeffler KU; Mangini NJ | title = Expression and immunolocalization of plasma membrane calcium ATPase isoforms in human corneal epithelium.| journal =Molecular Vision | volume =11 | issue = | pages = 169–178| publisher = | date =2005 | url =http://www.molvis.org/molvis/v11/a19/ | doi = | id = | accessdate = ]
The PMCA belongs to a family of
P-type primary ion transport ATPases that form an aspartyl phosphateintermediate.
The PMCA is expressed in a variety of tissues, including the
brain. cite journal | last =Jensen | first =TP | authorlink = | coauthors =Filoteo A; Knopfel T; Empson RM. | title =Pre-synaptic plasma membrane Ca2+ ATPase isoform 2a regulates excitatory synaptic transmission in rat hippocampal CA3 | journal =Journal of Physiology | volume = | issue = | pages =Published online ahead of print | publisher = | date =2006 | url =http://jp.physoc.org/cgi/rapidpdf/jphysiol.2006.123901v1| doi = | id =17170045 | accessdate =2007-01-13 ]
Sarcoplasmic reticulum Ca2+ ATPase (SERCA)
SERCA resides in the
sarcoplasmic reticulum(SR) within muscle cells. It is a Ca2+ ATPase which transfers Ca2+ from the cytosolof the cell to the lumen of the SR at the expense of ATP hydrolysisduring muscle relaxation.
* [http://www.utoronto.ca/maclennan/rint1.htm Overview at utoronto.ca]
* [http://www.sanger.ac.uk//cgi-bin/Pfam/getacc?PF00689 Cation transporting ATPase family in Pfam]
* - Calculated orientations of calcium ATPase in membrane
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