PMC

(a) Number of NOE upper distance limits per residue in the amino acid sequence of CRT(189–288). The intraresidual and sequential upper distance limits are displayed as white bars, medium-range constraints are gray, and long-range constraints are black. (b) Average local backbone rmsd in CRT(189–288). The rmsd values plotted at the position of residue i were calculated for the N, C^α, and C′ atoms of the tripeptide segments of residues i − 1, i, and i + 1.

Stereo views of the hydrophobic clusters in the CRT(189–288) structure. The local superpositions of the 20 conformers are for best fit of the backbone atoms N, C^α, and C′ of the following residues: (a) Lys-198, Pro-199, Trp-202, and Trp-272; (b) Lys-215, Pro-216, Trp-219, and Trp-258; (c) Lys-232, Pro-233, Trp-236, and Trp-244. The backbone segments, which do not coincide exactly with those used for the superpositions, are yellow. The amino acid side chains are colored as in Figs. and .

Alignment of the sequence repeats in rat CRT(189–288). The three 17-residue type 1 repeats are shown in yellow, and the three 14-residue type 2 repeats are white. The positions of the strands in three short antiparallel β-sheets are indicated by orange, red, and blue arrows above the sequence. The position of a helical turn, which includes a two-residue insert between the third and fourth repeat, is shown by a yellow cylinder above the sequence. Residues conserved in all three repeats of one type are underlined.

(a and b) Bundles of the 20 energy-minimized conformers used to represent the NMR structure of CRT(189–288). (a) Superposition for best fit of the backbone atoms N, C^α, and C′ of the residues 219–258. (b) Superposition for best fit of the backbone atoms N, C^α, and C′ of the residues 189–209 and 262–284. In each drawing the polypeptide segments used for the superposition are colored yellow, and the remaining residues are white. (c) Cartoon of the conformer from a for which the white region is on the extreme left. The β-sheets and the helical turn on the extreme right are represented by ribbons and colored as in Fig. . The same color code is used for the three associated hydrophobic clusters. The polypeptide segments that connect the β-strands are drawn as thin cylindrical rods, which are yellow for the type 1 repeats and white for the type 2 repeats. Figs. – were prepared by using the program molmol ().

(a) Superposition for best fit of the backbone atoms N, C^α, and C′ of the residues 223–253 in CRT(189–288). The backbone is yellow. The side chains are blue for positively charged residues, red for negatively charged residues, and white for hydrophobic and polar residues. The positions of selected residues are indicated. (b) Superposition for best fit for the residues 222–253 of the mean structures of CRT(189–288) (yellow) and CRT(189–261) (green) (rmsd = 1.98 Å). For each of the two structures a set of 20 conformers is shown, which have been fitted individually to the respective mean coordinates. (c and d) Surface views of CRT(189–288). Red indicates negative electrostatic charges and blue, positive electrostatic charges. The positions of selected residues are indicated. The orientation of the molecule in c corresponds to that in Fig. c, and the orientation in d was obtained by a 180° rotation about a horizontal axis.