Crambin crystal structure

Fig. 23.10 a, b. Comparison of fused water pentagons a in crambin and b in the clathrates of ethylene oxide deutero hydrate and of n-propylamine hydrate. Pentagon arrangements which are comparable in both crystal structures are indicated by thick lines [844]... 

Figure 5 Energetic minimization of the crystal structure of crambin. The minimization takes into consideration 1356 atoms. Elementary cell of the crystal structure illustration of the steepest descent minimization procedure result of the minimization with the force fields Amber and Amber/OPLS (rms root mean square deviation between observed and calculated structure) taken from Jorgensen and Tirado-Rives (1988).

Figure 3 Ramachandran diagrams for crambin, BPTI, turkey egg white lysozyme, and MbCO based on their X-ray crystal structures...

Tfeeter MM (1984) Water structure of a hydrophobic protein at atomic resolution pentagon rings of water molecules in crystals of crambin. Proc Natl Acad Sci USA 81 6014- 6018... 

Anomalous scattering can also be used directly if the protein is small and a suitable anomalous scatterer can be used. The three-dimensional structure of the small protein, crambin, was determined by W ayne A. Hendrickson and Martha Teeter by the use of anomalous dispersion measurements. This protein contains 45 amino acid residues and diffracts to 0.88 A resolution. It crystallizes with 72 water and four ethanol molecules per protein molecule. Since there is a sulfur atom in the protein molecule, the use of its anomalous scattering was made. The nearest absorption edge of sulfur lies at 5.02 A, but for Cu Ka radiation, wavelength 1.5418 A, values of A/ and A/" for sulfur are 0.3 and 0.557, respectively. Friedel-related pairs of reflections were measured to 1.5 A resolution, and sulfur atom positions were computed from difference Patterson maps. The structure is now fully refined and a portion of an a helix was shown in Figure 12.27 (Chapter 12). 

MPP-CRYSTAL has been used recently for the calculation of the FIF total energy of a small structural protein that has been characterized by X-ray diffraction studies (0.52 A) to a very high precision crambin, which has P2j symmetry with two chains per unit cell, 46 aminoacidic residues per chain, and 1284 atoms per cell. 

A strikingly similar yet different peptide has been isolated from seeds of the crucifer Crambe abyssinica, and is called crambin (11). This peptide contains only three disulfide bonds, whose positions correspond to those of viscotoxin (12). It is very hydrophobic, is not positively charged as are the other thionins and consequently is not toxic. Because of its hydrophobic nature it is easy to crystallize, and the three dimensional structure has been determined by X-ray and neutron diffraction (13). Its three dimensional structure is very similar to that determined for the related thionin a 1 -purothionin, as discussed below (14,15). 

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