Canadian Medical Guide > Chemicals and Drugs > Amino Acids, Peptides, and Proteins > Proteins > Carrier Proteins > Calcium-Binding Proteins Terms and Definitions

Calcium-Binding Proteins

Medical Definition:	Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.
Guide Notes:	RECEPTORS, CALCIUM-SENSING is also available
Previously Indexed:	Calcium (1966-1979),Carrier Proteins (1971-1979),Proteins (1966-1970)

Calcium-Binding Proteins Categories.

	Annexins - Family of calcium- and phospholipid-binding proteins which are structurally related and exhibit immunological cross-reactivity. Each member contains four homologous 70 kD repeats. The annexins are differentially distributed in vertebrate tissues (and lower eukaryotes) and appear to be involved in membrane fusion and signal transduction.
	Calcium-Binding Protein, Vitamin D-Dependent - A protein that plays a fundamental role in the Vitamin D mediated transport of calcium in reptiles, amphibians, birds and mammals. It is found in the intestine, kidneys, egg shell gland, brain, and possibly other organs. Its molecular weight is species dependent.
	Calmodulin - A heat-stable, low-molecular-weight activator protein found mainly in the brain and heart. The binding of calcium ions to this protein allows this protein to bind to cyclic nucleotide phosphodiesterases and to adenyl cyclase with subsequent activation. Thereby this protein modulates cyclic AMP and cyclic GMP levels.
	Calnexin - A lectin found in ENDOPLASMIC RETICULUM membranes that binds to specific N-linked OLIGOSACCHARIDES found on newly synthesized proteins. It may play role in PROTEIN FOLDING or retention and degradation of misfolded proteins in the endoplasmic reticulum.
	Calreticulin - A multifunctional protein that is found primarily within membrane-bound organelles. In the ENDOPLASMIC RETICULUM it binds to specific N-linked oligosaccharides found on newly-synthesized proteins and functions as a MOLECULAR CHAPERONE that may play a role in PROTEIN FOLDING or retention and degradation of misfolded proteins. In addition calreticulin is a major storage form for CALCIUM and functions as a calcium-signaling molecule that can regulate intracellular calcium HOMEOSTASIS.
	Calsequestrin - Acidic protein found in SARCOPLASMIC RETICULUM that binds calcium to the extent of 700-900 nmoles/mg. It plays the role of sequestering calcium transported to the interior of the intracellular vesicle.
	Gelsolin - A 90-kD protein produced by macrophages that severs actin filaments and forms a cap on the newly exposed filament end. Gelsolin is activated by calcium ions and participates in the assembly and disassembly of actin, thereby increasing the motility of some cells.
	Myosin Light Chains - The smaller subunits of MYOSINS that bind near the head groups of MYOSIN HEAVY CHAINS. The myosin light chains have a molecular weight of about 20 KD and there are usually one essential and one regulatory pair of light chains associated with each heavy chain. Many myosin light chains that bind calcium are considered "calmodulin-like" proteins.
	Osteocalcin - Vitamin K-dependent calcium-binding protein synthesized by osteoblasts and found primarily in bone. Serum osteocalcin measurements provide a noninvasive specific marker of bone metabolism. The protein contains three residues of the amino acid gamma-carboxyglutamic acid (Gla), which, in the presence of calcium, promotes binding to hydroxyapatite and subsequent accumulation in bone matrix.
	Osteonectin - Non-collagenous, calcium-binding glycoprotein of developing bone. It links collagen to mineral in the bone matrix. In the synonym SPARC glycoprotein, the acronym stands for Secreted Protein, Acidic and Rich in Cysteine.
	S100 Proteins - A family of highly acidic calcium-binding proteins found in large concentration in the brain and believed to be glial in origin. They are also found in other organs in the body. They have in common the EF-hand motif (EF-HAND MOTIFS) found on a number of calcium binding proteins. The name of this family derives from the property of being soluble in a 100% saturated ammonium sulfate solution.
	Troponin C - One of the three polypeptide chains that make up the TROPONIN complex of skeletal muscle. It is a calcium-binding protein.

Calcium-Binding Proteins Medical Definitions and Terms

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