Biomaterial Database

Temperature dependent chaperone-like activity of alpha-crystallin. 1995

B Raman, and T Ramakrishna, and C M Rao

Centre for Cellular and Molecular Biology, Hyderabad, India.

Alpha-crystallin, a multimeric protein present in the eye lens, is known to have chaperone-like activity in preventing the aggregation of enzymes and other crystallins. We have studied the chaperone-like activity of this protein towards the aggregation of insulin B chain, induced by reducing the interchain disulphide bond with dithiothreitol. At room temperature, there is no detectable protection (at a 1:1 (w/w) ratio of insulin: alpha-crystallin) against the aggregation of insulin B chain by alpha-crystallin, whereas it completely prevents this aggregation at 40 degrees C. We have monitored the temperature dependence of the protection of aggregation by alpha-crystallin; the protection increases sharply above 30 degrees C and reaches almost 100% by 41 degrees C. Probing the hydrophobic surfaces of alpha-crystallin with the hydrophobic fluorphore 8-anilino-1 naphthalene sulfonate suggests that the hydrophobic surfaces of alpha-crystallin are exposed to a greater extent above 30 degrees C. A complete prevention of the aggregation is achieved at 27.6 degrees C by increasing the concentration of alpha-crystallin by more than 8 fold. Similar temperature dependent chaperone-like activity of alpha-crystallin is observed towards the aggregation of zeta-crystallin, an enzyme crystallin from guinea pig. We have earlier shown that alpha-crystallin exposes hydrophobic surface(s) at temperatures above 30 degrees C. These results support our earlier hypothesis [Raman, B. and Rao, Ch.M. (1994) J. Biol. Chem. 269, 27264-27268] that the chaperone-like activity of alpha-crystallin is more pronounced in its structurally perturbed state.

UI	MeSH Term	Description	Entries
D007328	Insulin	A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).	Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D007908	Lens, Crystalline	A transparent, biconvex structure of the EYE, enclosed in a capsule and situated behind the IRIS and in front of the vitreous humor (VITREOUS BODY). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the CILIARY BODY is crucial for OCULAR ACCOMMODATION.	Eye Lens,Lens, Eye,Crystalline Lens
D002417	Cattle	Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.	Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D003459	Crystallins	A heterogeneous family of water-soluble structural proteins found in cells of the vertebrate lens. The presence of these proteins accounts for the transparency of the lens. The family is composed of four major groups, alpha, beta, gamma, and delta, and several minor groups, which are classed on the basis of size, charge, immunological properties, and vertebrate source. Alpha, beta, and delta crystallins occur in avian and reptilian lenses, while alpha, beta, and gamma crystallins occur in all other lenses.	Lens Proteins,Crystallin,Eye Lens Protein,Lens Protein, Eye,Protein, Eye Lens,Proteins, Lens
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D013050	Spectrometry, Fluorescence	Measurement of the intensity and quality of fluorescence.	Fluorescence Spectrophotometry,Fluorescence Spectroscopy,Spectrofluorometry,Fluorescence Spectrometry,Spectrophotometry, Fluorescence,Spectroscopy, Fluorescence
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular
D018833	Chaperonins	A family of multisubunit protein complexes that form into large cylindrical structures which bind to and encapsulate non-native proteins. Chaperonins utilize the energy of ATP hydrolysis to enhance the efficiency of PROTEIN FOLDING reactions and thereby help proteins reach their functional conformation. The family of chaperonins is split into GROUP I CHAPERONINS, and GROUP II CHAPERONINS, with each group having its own repertoire of protein subunits and subcellular preferences.	Chaperonin,Chaperonin Complex,Chaperonin Complexes,Chaperonin Family,Chaperonin Protein Complex,Complex, Chaperonin