Structure of Ribosomal Protein L6 from Escherichia coli

• Published in: European journal of biochemistry Vol. 127; no. 3; pp. 587 - 595
• Main Authors: STEINHÄUSER, Klaus G., WOOLLEY, Paul, EPE, Bernd, DIJK, Jan
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.10.1982
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1111/j.1432-1033.1982.tb06913.x

Protein L6 from the 50‐S ribosomal subunit has been investigated using fluorimetric techniques. The intrinsic fluorophore Trp‐61 and fluorescent labels (acetylaminoethyl‐dansyl and acetylaminofluorescein) attached to the residue Cys‐124 were used. It proved possible to incorporate fluorescence‐labelled L6 into the 50‐S ribosome. Trp‐61 is exposed to solvent, as shown by its emission wavelength and by quenching experiments; the latter also show that it lies in a pocket with a high positive charge due to the basic residues in the N‐terminal fragment. Cys‐124 lies in a less strongly positive region. Upon incorporation into the 50‐S subunit, the label on Cys‐124 becomes less accessible for quenching but its positive potential rises, showing the absence of direct contact with 23‐S RNA. Analysis of anisotropy data indicates a considerable degree of asphericity of free L6. Energy transfer between Trp‐61 and the dansyl label on Cys‐124, measured by donor quenching and acceptor enhancement, reveals a separation of 3.5 ± 0.4 nm (35 ± 4Å) between fluorophores.