protein Definition

any of various naturally occurring extremely complex substances that consist of amino-acid residues joined by peptide bonds, contain the elements carbon, hydrogen, nitrogen, oxygen, usually sulfur, and occasionally other elements (such as phosphorus or iron), and include many essential biological compounds (such as enzymes, hormones, or antibodies)

the total nitrogenous material in plant or animal substances

any of a class of enzymes that catalyze the transfer of a phosphate group from ATP to one or more amino acids in the side chain of a protein resulting in a conformational change affecting protein function

a protein kinase that catalyzes the phosphorylation of specific serine or threonine amino acid residues

a polypeptide composed of one or two antibody light chains that is found especially in the urine of persons affected with multiple myeloma

a compound of a protein with a nonprotein

a protein present in blood serum in various abnormal states (such as inflammation or neoplasia) —abbreviation CRP

a protein-rich food additive made from ground whole fish

any of a class of cell membrane proteins that are coupled to cell surface receptors and upon stimulation of the receptor by an extracellular signaling molecule (such as a hormone or neurotransmitter) bind to GTP to form an active complex which mediates an intracellular event (such as activation of adenylate cyclase)

any of a group of molecular chaperones that are produced especially in cells subjected to stressful conditions (such as high temperature) and that serve to stabilize proteins and ensure proper assembly and folding of proteins

a glycoprotein found especially on the cell surface of neurons in the brain and spinal cord that sometimes occurs in an abnormal misfolded form which proliferates by inducing the normal protein to convert to the misfolded pathogenic form —abbreviation PrP