Calcium sensor protein

Fig. 10.3. Acceptor photobleaching analysis of interaction between barley MLO and calmodulin. Barley MLO is a plant-specific integral membrane protein that associates with the cytosolic calcium sensor protein Calmodulin...

Caulfield MP, Jones S, Vallis Y, Buckley NJ, Kim GD, Milligan G, Brown DA (1994) Muscarinic M-current inhibition via G alpha q/11 and alpha-adrenoceptor inhibition of Ca2+ current via G alpha o in rat sympathetic neurones. J Physiol 477 Pt 3 415-22 Charvin N, L Eveque C, Walker D, Berton F, Raymond C, KataokaM, Shoji-Kasai Y, Takahashi M, De Waard M, Seagar MJ (1997) Direct interaction of the calcium sensor protein synaptotagmin I with a cytoplasmic domain of the alphal A subunit of the P/Q-type calcium channel. Embo J 16 4591-6... 

Calcium Sensor Protein Is Used in the Regulation of Plasma Ca Levels... 

Calcium sensor protein also occiurs in the kidney. Specifically, the calcium sensor occurs in the thick ascending loop, where the N-terminal half juts out into the extracellular fluid (not into the lumen of the tubule, but in the space between tubules). When extracellular Ca " ions increase in concentration, the thick ascending loop decreases its rate of calcium resorption (Chattopadhyay et al, 1996 Pearce and Thakkar, 1997 Pearce et al., 1996). The regulatory scenario in the kidney represents a mode of regulating the body s calcium balance that appears completely independent of vitamin D. The overall scenario is that, as extracellular Ca " increases, the parathyroid gland decreases its release of PTH, and the kidney reduces its reabsorption of calcium ions from the developing urine. 

A second class of neuronal calcium sensors is formed by the guanylate cyclase-activating protein (GCAP). The GCAPs are expressed only in the photoreceptor cells of the retina of vertebrates. Recoverins and GCAPs have antagonistic roles in phototransduction. 

Yang, J., McBride, S., Mak, D. O. etal. Identification of a family of calcium sensors as protein ligands of inositol trisphosphate receptor Ca(2+) release channels. Proc. Natl Acad. Sci. U.S.A. 99 7711-7716, 2002. 

Following these initial results, POWT was employed in the detection of protein conformational changes after a binding event. The protein used, calmodulin, is relatively small and functions as an intracellular calcium sensor in eukaryotic cells [26]. When calmodulin interacts with calcium, a large conformational change... 

Calcium effects. The biochemical effects of Ca "" in the cytoplasm are mediated by special Ca -binding proteins calcium sensors"). These include the annexins, calmodulin, and troponin C in muscle (see p. 334). Calmodulin is a relatively small protein (17 kDa) that occurs in all animal cells. Binding of four Ca "" ions (light blue) converts it into a regulatory element. Via a dramatic conformational change (cf 2a and 2b), Ca -calmodulin enters into interaction with other proteins and modulates their properties. Using this mechanism, Ca "" ions regulate the activity of enzymes, ion pumps, and components of the cytoskeleton. 

Neurofibrillary tangles, aluminum associate with, 36 416-417 Neuromodulin, 46 449 Neuromuscular blocking agents, 36 7 Neuron-specific calcium sensor (NCS) proteins, 46 457... 

Otterbein LR, Kordowska J, Witte-Hoffmann C, Wang CL, Dominguez R. 2002. Crystal structures of S100A6 in the Ca(2+)-free and Ca(2+)-bound states the calcium sensor mechanism of S100 proteins revealed at atomic resolution. Structure 10(4) 557-567. 

Fig. 4 Stages in synaptic vesicle exocytosis. Putative intermediate steps on the molecular pathway to synaptic vesicle fusion. Vesicle delivery and tethering to the presynaptic membrane most likely involves Rab-proteins and their effectors. So far, the nature of a speculative docking complex (dc) is unclear, but docking appears to be independent from SNARE proteins. In the primed state, SNAREs have assembled into a complex probably stabilized by complexin (Cpx). The fusion reaction is arrested until the intracellular calcium concentration increases. The putative calcium sensor for fast neurotransmitter release, synaptotagmin 1 (Syt), binds to intracellular calcium and in turn triggers fusion by associating with the presynaptic membrane and interacting with the SNARE complex, thereby displacing complexin (Tang et al. 2006).

Bigelow, D. J., and Squier, T. C. 2005. Redox modulation of cellular signaling and metabolism through reversible oxidation of methionine sensors in calcium regulatory proteins. Biochim. Biophys. Acta 1703 121-134. 

Negyessy L, Goldman-Rakic PS. 2005. Subcellular localization of the dopamine D2 receptor and coexistence with the calcium-binding protein neuronal calcium sensor-1 in the primate prefrontal cortex. J Comp Neurol 488 464-475. 

Amino acid sequences can be searchedfor the presence of internal repeats. Such internal repeats can reveal information about the history of an individual protein itself Many proteins apparently have arisen by duplication of a primordial gene followed by its diversification. For example, calmodulin, a ubiquitous calcium sensor in eukaryotes, contains four similar calcium-binding modules that arose by gene duplication (Figure 4.28). 

Figure 4.28. Repeating Motifs in a Protein Chain. Calmodulin, a calcium sensor, contains four similar units in a single polypeptide chain shown in red, yellow, blue, and orange. Each unit binds a calcium ion (shown in green). 

Calmodulin (CaM), a 17-kd protein with four calcium-binding sites, serves as a calcium sensor in nearly all eukaryotic... 

Calcium ion acts by binding to calmodulin and other calcium sensors. Calmodulin contains four calcium-binding modules called EF hands that recur in other proteins. Ca2+-calmodulin activates target proteins by binding to positively charged amphipathic helices. 

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