THE RIBOSOMAL NEIGHBORHOOD OF THE CENTRAL FOLD OF TRANSFER-RNA - CROSS-LINKS FROM POSITION-47 OF TRANSFER-RNA LOCATED AT THE A-SITE, P-SITEOR E-SITE

The naturally occurring nucleotide 3-(3-amino-3-carboxy-propyl)uridine (acp(3)U) at position 47 of tRNA-(Phe) from Escherichia coli was modi fied with a diazirine derivative and bound to ribosomes in the presenc e of suitable mRNA analogues under conditions specific for the ribosom al A, P or E sites. After photo-activation at 350 nm the cross-links t o ribosomal proteins and RNA were identified by our standard procedure s. In the 30S subunit protein S19 (and weakly S9 and S13) was the targ et of cross-linking from tRNA at the A site, S7, S9 and S13 from the P site and S7 from the E site. Similarly, in the 50S subunit L16 and L2 7 were cross-linked from the A site, L1, L5, L16, L27 and L33 from the P site and L1 and L33 from the E site. Corresponding cross-links to r RNA were localized by RNase H digestion to the following areas: in 16S rRNA between positions 687 and 727 from the P and E sites, positions 1318 and 1350 (P site) and 1350 and 1387 (E site); in the 23S rRNA bet ween positions 865 and 910 from the A site, 1845 and 1892 (P site), 18 92 and 1945 (A site), 2282 and 2358 (P site), 2242 and 2461 (P and E s ites), 2461 and 2488 (A site), 2488 and 2539 (all three sites) and 257 2 and 2603 (A and P sites). In most (but not all) cases, more precise localizations of the cross-link sites could be made by primer extensio n analysis.