Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the presence of MgATP or MgADP the E. coli chaperonin proteins, GroEL and GroES, form a stable asymmetric complex with a stoichiometry of two GroEL7:one GroES7: seven MgADP. The distribution of the ligands between the two heptameric GroEL rings is crucial to our understanding of the mechanism of chaperonin-assisted folding, being either cis (i.e. [GroEL7.MgADP7.GroES7]-[GroEL7]) or trans (i.e. [GroEL7.MgADP7]-[GroEL7.GroES7]. On the basis of cross-linking experiments with 8-azido-ATP and the heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP), it was suggested that GroES and MgADP are bound to the same GroEL ring which resists proteinase K digestion [Nature 366 (1993) 228-233]. However, we find that the SPDP-promoted cross linking of GroES and GroEL occurs in the absence of Mg2+, ADP or ATP, which are required for the formation of the asymmetric complex. Cross-linking is shown to occur only when the SPDP-modified GroES is co-precipitated with GroEL by trichloracetic acid. Furthermore, there are structural grounds for questioning whether SPDP can crosslink, in a physiologically relevant manner, an amino group of GroES with any of the cysteinyl groups of GroEL.
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PMID:On the distribution of ligands within the asymmetric chaperonin complex, GroEL14.ADP7.GroES7. 778 7

During heat shock, structural changes in proteins and membranes may lead to cell death. While GroE and other chaperone proteins are involved in the prevention of stress-induced protein aggregation and in the recovery of protein structures, a mechanism for short-term membrane stabilization during stress remains to be established. We found that GroEL chaperonin can associate with model lipid membranes. Binding was apparently governed by the composition and the physical state of the host bilayer. Limited proteolysis of GroEL oligomers by proteinase K, which removes selectively the conserved glycine- and methionine-rich C terminus, leaving the chaperonin oligomer intact, prevented chaperonin association with lipid membranes. GroEL increased the lipid order in the liquid crystalline state, yet remained functional as a protein-folding chaperonin. This suggests that, during stress, chaperonins can assume the functions of assisting the folding of both soluble and membrane-associated proteins while concomitantly stabilizing lipid membranes.
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PMID:Evidence for a lipochaperonin: association of active protein-folding GroESL oligomers with lipids can stabilize membranes under heat shock conditions. 912 70

The major heat shock protein, chaperonin 60, has been established to have intercellular signaling activity in addition to its established protein-folding function. Mycobacterium tuberculosis is one of a small proportion of bacteria to encode two chaperonin 60 proteins. We have demonstrated that chaperonin 60.1 from this bacterium is a very active stimulator of human monocytes. To determine structure/function relationships of chaperonin 60.1 we have cloned and expressed the apical, equatorial, and intermediate domains of this protein. We have found that the signaling activity of M. tuberculosis chaperonin 60.1 resides in the equatorial domain. This activity of the recombinant equatorial domain was completely blocked by treating the protein with proteinase K, ruling out lipopolysaccharide contamination as the cause of the cell activation. Blockade of the activity of the equatorial domain by anti-CD14 monoclonal antibodies reveals that this domain activates monocytes by binding to CD14. Looking at the oligomeric state of the active proteins, using native gel electrophoresis and protein cross-linking we found that recombinant M. tuberculosis chaperonin 60.1 fails to form the prototypic tetradecameric structure of chaperonin 60 proteins under the conditions tested and only forms dimers. It is therefore concluded that the monocyte-stimulating activity of M. tuberculosis Cpn60.1 resides in the monomeric subunit and within this subunit the biological activity is due to the equatorial domain.
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PMID:The intercellular signaling activity of the Mycobacterium tuberculosis chaperonin 60.1 protein resides in the equatorial domain. 1567 70