The crystal structure of the beta-lactamase of Streptomyces albus G has been solved at 0.3 nm resolution by X-ray-diffraction methods. The enzyme is a typical two-domain protein. One domain consists of five alpha-helices, and the other is five-stranded beta-sheet with alpha-helices on both sides of the sheet. The active-site serine residue (Ser-48) is within a cleft located between the two domains.

The crystal structure of a small calcium-binding protein, the parvalbumin I& from Opsanus tau in which Tb was substituted for Ca, has been analysed by multiwavelength anomalous diffraction. Data at a resolution of 2.3 A were collected at three wavelengths near the L, absorption edge of Tb (1.645-1.650 A), using the synchrotron radiation emitted by a storage ring and a multiwire proportional counter. The phases of the reflections were determined from this single derivative, without native data. Prior to any refinement, the resulting electron density map shows a good agreement with the model of the homologous carp parvalbumin in regions of identical amino-acid sequence.

Flock House virus, purified from infected cultured Drosophila cells, crystallizes into three different forms under identical growth conditions. Two crystal forms grow in the trigonal space group R3, both with equivalent cell constants a = 323.6 A, alpha = 61.7 degrees. The difference between the two trigonal crystal forms is 1.1 degrees in the orientation of the virus particle as determined from the rotation function. Early crystal setups grew in one form, while recent crystals grew in the other form. The third space group, which accounts for 5% of the observed crystals and grows with both trigonal forms, is orthorhombic I222 with cell parameters a = 416.7, b = 332.1, c = 351.2 A. The trigonal crystal forms contain one virion per unit cell and the orthorhombic form contains two particles per cell. All three crystal forms diffract X-rays to 2.8 A resolution.

Toadfish muscle parvalbumin I& can bind two Tb3+ which displace the two Caz+ normally bound. This terbium derivative was crystallized with space group P2,2,2 and lattice constants a= 56.2 A, b = 59.5 A and c = 27.2 A. The structure at 3.2 A resolution was determined applying a molecular replacement method and using the known co-ordinates of carp Caz+-parvalbumin. The structure was refined to a conventional R factor of 26 % for 1166 reflections in the resolution range 3.2-6 A. The a-carbon backbone of the structures of toadtish and carp parvalbumins are very similar.Crystal X-ray crystallography Three-dimensional structure TF+ Parvalbumin Ca2+-binding site