PMID:7789507
| Citation |
Girshovich, AS, Bochkareva, ES, Todd, MJ and Lorimer, GH (1995) On the distribution of ligands within the asymmetric chaperonin complex, GroEL14.ADP7.GroES7. FEBS Lett. 366:17-20 |
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| Abstract |
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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| Keywords |
Adenosine Diphosphate/metabolism; Binding Sites; Chaperonin 10/metabolism; Chaperonin 60/chemistry; Chaperonin 60/metabolism; Cross-Linking Reagents; Cysteine/chemistry; Escherichia coli/metabolism; Ligands; Macromolecular Substances; Models, Molecular; Protein Conformation; Protein Folding; Protein Structure, Secondary; Succinimides |
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