protein
DEFINITION:
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.
binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).
carrier proteins - A binding protein (See above).
plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.
transport protein - binding protein (See above).
protein
DEFINITION:
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.
binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).
carrier proteins - A binding protein (See above).
plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.
transport protein - binding protein (See above).
protein
DEFINITION:
Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.
binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).
carrier proteins - A binding protein (See above).
plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.
transport protein - binding protein (See above).
factor
DEFINITION:
1. Any of several substances or activities that are necessary to produce a result, e.g., a coagulation factor (see below). Often, use of the term "factor" indicates that the chemical nature of the substance or its mechanism of action is unknown, as in endocrinology, where "factors" are renamed as "hormones" when their chemical nature is determined.
2. One of two or more quantities that multiplied together form a product.
3. A gene (hereditary factor).
Antihemophilic Factor (AHF) -
1. See Factor VIII under coagulation factor (below).
2. [USP] A sterile freeze-dried powder containing the Factor VIII fraction prepared from units of human venous plasma obtained from suitable whole-blood donors; it may contain heparin sodium or sodium citrate. Used to arrest hemorrhage or to prevent hemorrhage during surgery or other procedures in patients with hemophilia A; administered intravenously.
Coagulation Factors - Substances in the blood that are essential to the clotting process and hence, to the maintenance of normal hemostasis. They are designated by Roman numerals, to which the notation "a" is added to indicate the activated state. Platelet factors (see below), designated by Arabic numerals, also play a role in coagulation.
Coagulation Factor II, prothrombin - A plasma protein that is converted to the active form thrombin (factor IIa) by cleavage by activated factor X (Xa) in the common pathway of blood coagulation; thrombin then cleaves fibrinogen to its active form fibrin. Deficiency of the factor leads to hypoprothrombinemia.
Coagulation Factor III, tissue thromboplastin - A lipoprotein functioning in the extrinsic pathway of blood coagulation, activating factor X (see below).
Coagulation Factor V, proaccelerin - A heat- and storage-labile material, present in plasma but not in serum, functioning in both the intrinsic and extrinsic pathways of blood coagulation. Deficiency of this factor, an autosomal recessive trait, leads to a rare hemorrhagic tendency, known as Owren's disease or parahemophilia, which varies greatly in severity.
Coagulation Factor VIII, antihemophilic factor (AHF) - A relatively storage-labile factor (see below) participating only in the intrinsic pathway of blood coagulation. Deficiency of this factor, when transmitted as a sex-linked recessive trait, causes classical hemophilia (hemophilia A). (See also antihemophilic factor above.)
Coagulation Factor IX, plasma thromboplastin component (PTC) - A relatively storage-stable substance involved in the intrinsic pathway of blood coagulation; upon activation, it activates factor X (see below). Deficiency results in a hemorrhagic syndrome called hemophilia B, resembling hemophilia A. Called also autoprothrombin II, Christmas factor, and antihemophilic factor B.
Coagulation Factor X, Stuart factor - A storage-stable factor that participates in both the intrinsic and extrinsic pathways of blood coagulation, uniting them to begin the common pathway of coagulation. Once activated, it forms a complex with calcium, phospholipid, and factor V (see above); the complex (prothrombinase) can cleave and activate prothrombin to thrombin. Deficiency of this factor may cause a systemic coagulation disorder.
Coagulation Factor XI, plasma thromboplastin antecedent (PTA) - A stable factor involved in the intrinsic pathway of blood coagulation; once activated, it activates factor IX. Deficiency of this factor results in a systemic blood-clotting defect called hemophilia C, which may resemble hemophilia A. Called also antihemophilic factor C.
Coagulation Factor XII, Hageman factor - A stable factor activated by contact with glass or other foreign surfaces, which initiates the intrinsic process of blood coagulation by activating factor XI and participates in activation of the kinin and fibrinolytic pathways. Deficiency of this factor results in a tendency toward thrombotic disorders, due to lack of activation of the fibrinolytic pathway. Called also glass factor, contact factor, or activation factor.
Heat-labile Factor - See Factor V under Coagulation Factors (above).
Platelet Factor - Factors important in hemostasis which are contained in or attached to the platelets.
Storage-labile Factor - A factor which shows chemically-unstable attributes during storage.
von Willebrand Factor (vWF) - The attribute of factor VIII (see above) necessary for the adhesion of platelets to vascular elements. Deficiency of this factor results in the prolonged bleeding time seen in von Willebrand's disease.
While aquaporin-2 (AQP2) abundance is chiefly controlled by [8-arginine]vasopressin (AVP) through cAMP-inducible AQP2 gene transcription, other factors largely contribute to adjust the levels of AQP2 protein, and thus water excretion, to meet the organism’s daily needs. The mpkCCDcl4 immortalized collecting duct (CD) principal cell line exhibits many major functional properties of CD principal cells including AVP-inducible expression of endogenous AQP2 mRNA and protein. RNase protection assay, Real-time PCR analysis and Western blot analysis of whole cell AQP2 expression in this cell line revealed that both AQP2 transcription and mRNA translation provide a means by which AQP2 expression may be controlled. Protein degradation analysis revealed that AQP2 protein is quickly degraded via both lysosomal and proteasomal degradation pathways. In addition to the stimulatory effect mediated by AVP on AQP2 transcription, AVP was found to buffer the increase in AQP2 protein content by negatively-acting on AQP2 protein turn-over. The influence of several AVP-independent factors were also investigated. Aldosterone was found to decrease AQP2 mRNA expression levels but increased AQP2 protein abundance by increasing protein turnover. Insulin was also found to significantly increase AQP2 protein content by potentiating AVP-inducible AQP2 mRNA expression. Expression levels of both AQP2 mRNA and protein were found to decrease shortly (< 3h) following osmotic shock and to increase after longer exposure times (> 8 h) in response to hypertonicity. Like insulin, neither osmotic shock nor hypertonicity were found to alter AQP2 protein turn-over. The identification of molecular factors that modulate AQP2 abundance in response to extracellular factors would lend important support to our understanding of water handling. Among other candidate factors, investigation of the tonicity-responsive enhancer binding protein (TonEBP) in hypertonic-upregulation of AQP2 mRNA is currently under way.