Zero-length cross-linking of the C-terminal domain of Escherichia coli ribosomal protein L7/L12 to L10 in the ribosome and in the (L7/L12)4-L10 pentameric complex

• Published in: Biochimie Vol. 75; no. 11; p. 963
• Main Authors: Makarov, E M, Oleinikov, A V, Zecherle, G N, Traut, R R
• Format: Journal Article
• Language: English
• Published: France 1993
• Subjects: Binding Sites; Chromatography, Gel; Chromatography, High Pressure Liquid; Cross-Linking Reagents; Cysteine - chemistry; Disulfides - chemistry; Electrophoresis, Polyacrylamide Gel; Escherichia coli - chemistry; Immunoblotting; Protein Conformation; Ribosomal Proteins - chemistry; Ribosomes - chemistry; Sulfhydryl Reagents - chemistry
• ISSN: 0300-9084
• DOI: 10.1016/0300-9084(93)90146-J

L7/L12Cys89 is a variant of L7/L12 that has a single cysteine residue located in the C-terminal domain in which Cys89 is the only cysteine residue in the protein. A cross-link between this site and the single cysteine in L10, residue 70, was formed with 1,4-di[3'-(2'-pyridyldithio)-propionamido]butane, a sulfhydryl-specific homobifunctional reagent of maximum length 16 A. It is now shown that a zero-length disulfide cross-link between L7/L12Cys89 and L10Cys70 is formed by mild oxidation with Cu2+(phenanthroline)3 of either intact ribosomes or the stable, pentameric complex (L7/L12)4-L10. The formation of the zero-length cross-link defines more closely the contact between the two proteins. Protein L10 is located at the base of the L7/L12 stalk where it provides binding sites for the N-terminal domains of both dimers of L7/L12. The L7/L12Cys89-L10Cys70 cross-link lends further support to our previous model that places at least one of the two dimers of L7/L12 on the surface of the body of the 50S subunit in a bent conformation with the C-terminal domain in close proximity to its N-terminal domain, at the base of the L7/L12 stalk. The L7/L12Cys89-L10Cys70 cross-link in the pentameric L8 complex implies that the protein can exist in this bent conformation there as well as in the ribosome.