Topography of the Escherichia coli Initiation Factor 2/fMet-tRNAfMet Complex as Studied by Cross-Linking

Abstract
trans-Diamminedichloroplatinum(II) was used to induce reversible cross-links between Escherichia coli initiation factor 2 (IF-2) and fMet-tRNAfMet. Two distinct cross-links between IF-2 and the initiator tRNA were produced. Analysis of the cross-linking regions on both RNA and protein moieties reveals that the T arm of the tRNA is in the proximity of a region of the C-terminal domain of IF-2 (residues Asn611−Arg645). This cross-link is well-correlated with the fact that the C-domain of IF-2 contains the fMet-tRNA binding site and that the cross-linked RNA fragment precisely maps in a region which is protected by IF-2 from chemical modification and enzymatic digestion. Rather unexpectedly, a second cross-link was characterized which involves the anticodon arm of fMet-tRNAfMet and the N-terminal part of IF-2 (residues Trp215−Arg237).