Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the effects of the Sulfolobus solfataricus chaperonin on the aggregation and inactivation upon heating of four model enzymes: chicken egg white lysozyme (one 14.4-kDa chain), yeast alpha-glucosidase (one 68.5-kDa chain), chicken liver malic enzyme (four 65-kDa subunits), and yeast alcohol dehydrogenase (four 37.5-kDa subunits). When the proteins were heated in the presence of an equimolar amount of chaperonin, 1) the aggregation was prevented in all solutions; 2) the inactivation profiles of the single-chain enzymes were comparable with those detected in the absence of the chaperonin, and enzyme activities were regained in the solutions heated in the presence of the chaperonin upon ATP hydrolysis (78 and 55% activity regains for lysozyme and alpha-glucosidase, respectively); 3) the inactivation of the tetrameric enzymes was completely prevented, whereas the activities decreased in the absence of the chaperonin. We demonstrate by gel filtration chromatography that the chaperonin interacted with the structures occurring during thermal denaturation of the model proteins and that the interaction with the single-chain proteins (but not that with the tetrameric proteins) was reversed upon ATP hydrolysis. The chaperonin had nonequivalent surfaces for the binding of the model proteins upon heating: the thermal denaturation intermediates of the single-chain proteins share Surfaces I, while the thermal denaturation intermediates of the tetrameric proteins share Surfaces II. ATP binding to the chaperonin induced a conformation that lacked Surfaces I and carried Surfaces II. These data support the concept that chaperonins protect native proteins against thermal aggregation by two mechanistically distinct strategies (an ATP-dependent strategy and an ATP-independent strategy), and provide the first evidence that a chaperonin molecule bears functionally specialized surfaces for the binding of the protein substrates.
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PMID:Prevention of in vitro protein thermal aggregation by the Sulfolobus solfataricus chaperonin. Evidence for nonequivalent binding surfaces on the chaperonin molecule. 749 1

We have purified to apparent homogeneity and characterized a molecular chaperonin GroEL homologue (hpGroEL) from a moderately halophilic eubacterium, Pseudomonas sp. #43. Although this halophilic bacterium requires 1-2 M NaCl for growth, hpGroEL did not require a high concentration of salt for its stability, ATPase activity and refold-promoting activity for denatured protein. The ATPase activity was even more halo-sensitive than that of GroEL from Escherichia coli. The hpGroEL protein promotes Mg(2+)-ATP-dependent refolding of urea-denatured alpha-glucosidase in the presence of E. coli-GroES, indicating that chaperonins 60 and 10 isolated from halophilic and nonhalophilic eubacteria, respectively, can cooperate with each other.
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PMID:Purification and characterization of a GroEL homologue from the moderately eubacterial halophile Pseudomonas sp. #43. 923 26

The archaeon Methanopyrus kandleri is the most thermophilic methanogen presently known. It contains a chaperonin (thermosome) which represents a 951 kDa homo-hexadecameric protein complex with NH4+-dependent ATPase activity. Since its synthesis is not increased upon heat shock, we set out to test its chaperone function. In order to obtain the chaperonin in amounts sufficient for functional investigations, the gene encoding the 60 kDa subunit was expressed in E. coili BL21 (DE3) cells. Purification yielded soluble, high-molecular-mass double-ring complexes, indistinguishable from the natural thermosome. In order to study the functional properties of the recombinant protein complex, pig citrate synthase, yeast alcohol dehydrogenase, yeast alpha-glucosidase, bovine insulin, and Thermotoga phosphoglycerate kinase were used as model substrates. The results demonstrate that the recombinant M. kandleri thermosome possesses a chaperone-like activity in vitro, inhibiting aggregation as the major off-pathway-reaction during thermal unfolding and refolding of proteins after chemical denaturation. However, the chaperonin only forms dead-end complexes with its non-native substrates, no release is detectable at temperatures between 25 and 60 degrees C.
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PMID:The recombinant thermosome from the hyperthermophilic archaeon Methanopyrus kandleri: in vitro analysis of its chaperone activity. 1006 37