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Calcium-binding proteins can be either intracellular and extracellular. Those that are intracellular can contain or lack a structural EF-hand domain. Extracellular calcium-binding proteins are classified into six groups. [2] Since Ca (2+) is an important second messenger, it can act as an activator or inhibitor in gene transcription.
Calmodulin is a small, highly conserved protein that is 148 amino acids long (16.7 kDa). The protein has two approximately symmetrical globular domains (the N- and C- domains) each containing a pair of EF hand motifs [5] separated by a flexible linker region for a total of four Ca 2+ binding sites, two in each globular domain. [6]
Many of Ca 2+ mediated events occur when the released Ca 2+ binds to and activates the regulatory protein calmodulin. Calmodulin may activate the Ca 2+-calmodulin-dependent protein kinases, or may act directly on other effector proteins. [15] Besides calmodulin, there are many other Ca 2+-binding proteins that mediate the biological effects of ...
The α 1 subunit forms the Ca 2+ selective pore, which contains voltage-sensing machinery and the drug/toxin-binding sites. A total of ten α 1 subunits that have been identified in humans: [1] α 1 subunit contains 4 homologous domains (labeled I–IV), each containing 6 transmembrane helices (S1–S6). This arrangement is analogous to a homo ...
The plasma total calcium concentration is in the range of 2.2–2.6 mmol/L (9–10.5 mg/dL), and the normal ionized calcium is 1.3–1.5 mmol/L (4.5–5.6 mg/dL). [4] The amount of total calcium in the blood varies with the level of plasma albumin, the most abundant protein in plasma, and therefore the main carrier of protein-bound calcium in the blood.
Thus, rise in extracellular Ca2+ ions may serve to prime the integrin heterodimer. The release of intracellular Ca2+ have been shown to be important for integrin inside-out activation. [16] However, extracellular Ca2+ binding may exert different effects depending on the type of integrin and the cation concentration. [17]
Calcium imaging is a microscopy technique to optically measure the calcium (Ca 2+) status of an isolated cell, tissue or medium.Calcium imaging takes advantage of calcium indicators, fluorescent molecules that respond to the binding of Ca 2+ ions by fluorescence properties.
Ca 2+ binding to these regulatory domains activates the transport of Ca 2+ across the plasma membrane. The structure of CBD1 shows four Ca 2+ ions arranged in a tight planar cluster. The structure of CBD2 in the Ca 2+ -bound (1.7 Å resolution) and Ca 2+ -free (1.4 Å resolution) conformations shows (like CBD1) a classical Ig fold but ...