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On the distribution of ligands within the asymmetric chaperonin complex, GroEL 14 · ADP 7 · GroES 7
Author(s) -
Girshovich Alexander S.,
Bochkareva Elena S.,
Todd Matthew J.,
Lorimer George H.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00479-s
Subject(s) - chaperonin , groel , groes , chemistry , protein folding , biochemistry , escherichia coli , gene
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 GroEL 7 :one GroES 7 : 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. [GroEL 7 ·MgADP7·GroES 7 ]‐[GroEL 7 ]) or trans (i.e. [GroEL 7 · MgADP 7 ]‐[GroEL 7 ·GroES 7 ]. 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 Mg 2+ , 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.