protein /pro·tein/ (pro´tēn) any of a group of complex organic compounds containing carbon, hydrogen, oxygen, nitrogen, and sulfur. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist of α-amino acids joined by peptide linkages. Twenty different amino acids are commonly found in proteins, each protein having a unique, genetically defined amino acid sequence that determines its specific shape and function. Their roles include enzymatic catalysis, transport and storage, coordinated motion, nerve impulse generation and transmission, control of growth and differentiation, immunity, and mechanical suppport.
acute phase protein any of the non-antibody proteins found in increased amounts in serum during the acute phase response, including C-reactive protein and fibrinogen.
amyloid precursor protein
(APP) a large transmembrane glycoprotein expressed on the cell surface and of uncertain function; endocytosis and cleavage can produce abnormal 40 to 43 amino acid peptides which aggregate to form A
, associated with Alzheimer's disease
Bence Jones protein a low-molecular-weight, heat-sensitive urinary protein found in multiple myeloma, which coagulates when heated to 45°–55°C and redissolves partially or wholly on boiling.
1. any protein able to specifically and reversibly bind other substances, such as ions, sugars, nucleic acids, or amino acids; they are believed to function in transport.
protein C a vitamin K–dependent plasma protein that, when activated by thrombin, inhibits the clotting cascade by enzymatic cleavage of factors V and VIII and also enhances fibrinolysis. Deficiency results in recurrent venous thrombosis.
C4 binding protein a complement system regulatory protein that inhibits activation of the classical pathway.
complete protein one containing the essential amino acids in the proportion required in the human diet.
compound protein , conjugated protein any of those in which the protein is combined with nonprotein molecules or prosthetic groups other than as a salt; e.g., nucleoproteins, glycoproteins, lipoproteins, and metalloproteins.
C-reactive protein a globulin that forms a precipitate with the C-polysaccharide of the pneumonococcus; the most predominant of the acute phase proteins.
cystic fibrosis transmembrane regulator protein
a transmembrane protein produced by the cystic fibrosis
gene, primarily functioning as a chloride channel. Numerous mutated forms of the gene have been associated with clinical cystic fibrosis
fibrillar protein any of the generally insoluble proteins that comprise the principal structural proteins of the body, e.g., collagens, elastins, keratin, actin, and myosin.
G protein any of a family of proteins of the intracellular portion of the plasma membrane that bind activated receptor complexes and, through conformational changes and cyclic binding and hydrolysis of GTP, effect alterations in channel gating and so couple cell surface receptors to intracellular responses.
glial fibrillary acidic protein (GFAP) the protein forming the glial filaments of the astrocytes and used as an immunohistochemical marker of these cells.
globular protein any of the water-soluble proteins yielding only α-amino acids on hydrolysis, including most of the proteins of the body, e.g., albumins and globulins.
guanyl-nucleotide-binding protein G p.
heat shock protein any of a group of proteins first identified as synthesized in response to hyperthermia, hypoxia, or other stresses and believed to enable cells to recover from these stresses. Many have been found to be molecular chaperones and are synthesized abundantly regardless of stress.
HIV proteins proteins specific to the human immunodeficiency virus; presence of certain specific HIV proteins together with certain HIV glycoproteins constitutes a serological diagnosis of HIV infection.
incomplete protein one having a ratio of essential amino acids different from that of the average body protein.
membrane cofactor protein (MCP) an inhibitor of complement activation found in most blood cells, endothelial and epithelial cells, and fibroblasts.
myeloma protein any of the abnormal immunoglobulins or fragments, such as Bence-Jones proteins, secreted by myeloma cells.
plasma proteins all the proteins present in the blood plasma, including the immunoglobulins.
(PrP) a protein of uncertain function, in humans coded for by a gene on the short arm of chromosome 20. The protease
-resistant core is the functional, and perhaps only, component of prions; several abnormal forms have been identified and are responsible for prion disease
a vitamin K–dependent plasma protein that inhibits blood clotting by serving as a cofactor for activated protein C
serum proteins proteins in the blood serum, including immunoglobulins, albumin, complement, coagulation factors, and enzymes.
serum amyloid A protein
SAA p.; a high-molecular-weight protein synthesized in the liver; it is an acute phase protein
and circulates in association with HDL lipoprotein. It is the precursor to AA amyloid
and accumulates in inflammation.
sphingolipid activator protein (SAP) any of a group of non-enzymatic lysosomal proteins that stimulate the actions of specific lysosomal hydrolases by binding and solubilizing their sphingolipid substrates.
transport protein a protein that binds to a substance and provides a transport system for it, either in the plasma or across a plasma membrane.
Etymology: Gk, proteios, first rank
any of a large group of naturally occurring complex organic nitrogenous compounds. Each is composed of large combinations of amino acids (usually 50 or more) containing the elements carbon, hydrogen, nitrogen, oxygen, and occasionally sulfur, phosphorus, iron, iodine, or other essential constituents of living cells. Twenty-two amino acids have been identified as vital for proper growth, development, and maintenance of health. The body can synthesize 13 of these, the nonessential amino acids, whereas the remaining 9 must be obtained from dietary sources and are termed essential. Protein is the major source of building material for muscles, blood, skin, hair, nails, and the internal organs. It is necessary for the formation of many hormones, enzymes, and antibodies and may act as a source of energy. Rich dietary sources are meat, poultry, fish, eggs, milk, and cheese, which are classified as complete proteins because they contain the nine essential amino acids. Nuts and legumes, including navy beans, chickpeas, soybeans, and split peas, are also good sources but are incomplete proteins because they do not contain all the essential amino acids in adequate amounts. Protein deficiency causes abnormal growth and tissue development in children, leading to kwashiorkor, whereas in adults it results in lack of vigor and stamina, weakness, mental depression, poor resistance to infection, impaired healing of wounds, and slow recovery from disease. Excessive intake of protein may in some conditions result in fluid imbalance.
the ratio of protein to creatinine in the urine, calculated as a measure of proteinuria.
any large organic compound made from one or more polypeptides, which are chains of amino
acids joined in a genetically determined order by peptide linkages between the carboxyl group of one amino acid and the amino group of the next. They contain carbon, hydrogen, oxygen and nitrogen and usually sulfur, occasionally phosphorus.
Proteins form a large and essential part of the body mass, comprising especially cell membranes, connective tissue, muscles, enzymes, hormones, blood proteins. To maintain this mass the diet must contain a high proportion of protein, especially in growing animals and those recovering from debilitating diseases.
a surface protein of Staphylococus aureus which binds to the Fc region of some IgG molecules. Fluorochrome-labeled protein A is used in an indirect immunofluorescence test for detecting bound immunoglobulins.
a recombinant protein with all its naturally occurring properties.
the portion of dietary protein that can be used by the animal.
a property of many drugs which limits their distribution and availability in the blood, as well as affecting elimination from the body.
a circulating vitamin K-dependent protein with anticoagulant effects. Promotes fibrinolysis.
calories derived from proteins in the diet.
protein calorie malnutrition
inadequate protein in the diet leads to impaired cell-mediated immunity, delayed wound healing and loss of lean body mass.
the number of calories provided from protein sources, compared with the total caloric intake; an indication of the level of protein intake.
one which, when coupled to a hapten, renders it capable of eliciting an immune response.
one containing the essential amino acids in the proportion required in the diet.
feeds containing a high concentration of protein, e.g. legume grains and forages, meat meal, fish meal, oil cakes, milling residues including bran, shorts, middlings, brewer's grains.
those in which the protein molecule is united with nonprotein molecules or prosthetic groups, e.g. glycoproteins, lipoproteins and metalloproteins.
in urine is valuable in correcting for variation in urine contents due to variable dilutions.
the total nitrogen content of a feed multiplied by 6.25. Includes several obvious errors but is still a close approximation of the protein content.
is usually the most expensive part of the diet, except for animals at pasture, and the constituent most likely to be deficient. An excess of protein in the diet in ruminants can cause a sharp rise in alkalinity, due to the release of ammonia, of the ruminal contents causing ruminal atony and indigestion.
the crude protein ingested less the protein excreted in the feces. The estimation requires a digestibility trial involving animals.
said of a feed. The total nitrogen content expressed as protein if it were all in that form. That is the percentage nitrogen in the feed multiplied by the average percentage of nitrogen in plant protein (6.25%).
protein excretion t
one that uses 51Cr-labeled protein which measures protein excretion in the feces in cases of protein-losing enteropathy.
characterized by shape, structure and low water solubility; they have a structural role. Examples are collagen
in recombinant DNA technology when a foreign gene is inserted into a plasmid vector to interrupt a gene, such as lacZ, the mRNA transcript of the recombinant plasmid contains the lacZ Shine-Dalgarno sequence and codons for the 3′ end of the lacZ gene protein followed by the codons of the foreign gene; the protein expressed is a fusion protein containing a few N-terminal lacZ amino acids and the contiguous foreign protein.
pharmaceutical preparations used in the treatment of severe, acute protein loss. Available for use orally or parenterally. They are partly digested proteins and contain a mixture of polypeptides, amino acids and other breakdown products.
an ordered set of small samples of proteins immobilized on a microscope slide or other solid surface that is used to determine protein-protein interactions.
protein nutritional deficiency
causes lack of muscle development, and slow growth rate and maturation. In adults there is a low milk production and poor weight gain. In severe states tissue and blood levels fall, hypoproteinemic edema may occur, and a degree of immunosuppression could be expected.
one having a ratio of essential amino acids different from that of the average body protein.
any protein located in the membrane but not essential to the reconstitution of that protein.
all the proteins present in the blood plasma, including the immunoglobulins. See plasma
polyhedrin matrix protein
a protein that comprises the major component of occlusion bodies produced by nuclear polyhedrosis virus and cytoplasmic polyhedrosis virus; the strong polyhedrin promoter is utilized in the expression of recombinant proteins in baculovirus expression systems.
rec A protein
an enzyme that binds to DNA and plays an important role in genetic recombination.
a circulating vitamin K-dependent protein with anticoagulant effects.
proteins in the blood serum, including immunoglobulins, albumin, complement, coagulation factors and enzymes.
protein shock anaphylaxis
occurring after the intravenous injection of protein.
in times of energy deficiency the animal body may raid protein stores for glucogenic amino acids, thus depleting body stores of proteins. Substances such as acetic acid which can fill the energy deficiency and avoid the protein loss are known as protein-sparing.
feeds which contain more than 20% protein.
proteins encoded by the viral genome.
Patient discussion about protein
Q. I get about 190 grams of protein a day. Is that too much protein? Have you ever seen a guy living only for food? No? Here I am. I get about 190 grams of protein a day. Is that too much protein? My weight is 183 pounds.
A. this is a good amount, just make sure that you get the majority of it from real foods and not from powders and bars.
Q. Does the cooking have a negative effect on the protein content of the food? I have heard that high temperatures cooking breaks the protein, so does the cooking have a negative effect on the protein content of the food?
A. Yes. Proteins can be denatured by heat, but only when the protein structure is delicate or is exposed to extremely high temperatures for long time. You must remember that breaking of protein is the physical-chemical process where the physical or chemical structure of a protein is rearranged. So cooking will not reduce on the nutritive value of the food until it’s cooked at cooking temperatures.
Q. Is it true that Casein protein can cause Cancer, or is harmful to the human body? Someone left a comment on my blog about Casein protein being bad for the body and that it could lead to Cancer. Is this true?
A. I am not familiar with such information, Casein is a protein that is found in large amounts in breastmilk and milk products replacements for babies and as far as I know it has no such affect.More discussions about protein