Figure 6.

(A) Activities of Tat fusions containing R₆QR₇, R₆NR₇, Rev₁₄, a Rev₁₄(N→Q) mutant, and Arg₁₄. Activities were determined as in Fig. 5B. (B) Apparent K_ds and α-helical content of R₆QR₇ and R₆NR₇ peptides. Apparent K_ds were measured by gel shift assays in the presence of tRNA by using wild-type RRE IIB RNA or a G46:C74→C:G mutant to assess nonspecific binding (affinities in the absence of tRNA competitor are substantially higher; ref. 3). Helical content was estimated from circular dichroism ellipticity at 222 nm (3). (C) Interaction of the carboxamide group of Asn-40 with the RRE G47:A73 bp, as determined by NMR (6, 7).