The structure of the A. fulgidus L7Ae–RNA complex. X-ray crystal structure of AfL7Ae bound to the k-turn of the l7ae 5′-UTR k-turn. The RNA (sequence shown at top) contains two copies of the potential k-turn related by twofold rotational symmetry. The two nucleotide changes were made to create full base-pairing at −3n and 5n; these are highlighted in blue. Our standard color-coding has been used for the k-turn, with the G:A base pairs green, the C and NC helices gray and yellow, respectively, and the loop magenta. This color scheme is also used in the structural images. The molecular graphics are shown as parallel-eye stereoscopic images. (A) The overall structure of the complex. The L7Ae protein is shown in cartoon form colored orange apart from the recognition helix and hydrophobic loop that are highlighted in cyan. Important amino acid side chains are shown in stick form. (B) The protein–RNA interactions in greater detail. The recognition helix (r-helix) is located in the widened major groove on the outer face of the k-turn, and the side chains of E34 and N33 are hydrogen bonded to the nucleobases of G1b and G2n, respectively. The hydrophobic loop (h-loop) sits over the L2, L1 region of the k-turn.
