Crystallization and preliminary X-ray investigation of recombinant human interleukin 10.

Crystals of recombinant human interleukin 10 have been grown from solutions of ammonium sulfate. The crystals are tetragonal, space group P4(1)2(1)2 or P4(3)2(1)2; the unit cell axes are a = 36.5 A and c = 221.9 A. There is the equivalent of one polypeptide chain in the asymmetric unit. The crystals are stable to X-rays and diffract to at least 2.5 A resolution.

Biochemical characterization of the proteins of Paramecium secretory granules.

The proteins of trichocysts (secretory granules) from Paramecium tetraurelia have been biochemically characterized. Two-dimensional electrophoresis revealed 34 major components and at least 120 minor components, most with molecular weights ranging from 14,000 to 21,000 and isoelectric points ranging from 4.8 to 5.2. Comparison of two-dimensional electrophoretic patterns of trichocysts before and after exocytosis revealed only minor changes in these patterns, although the protein matrix undergoes a striking change in morphology. To clarify the interrelationships among trichocyst proteins, two proteins from extruded trichocyst matrix were purified to homogeneity and sequenced at their N termini. Their sequences are distinct, but they share limited homology.

Selection of chemical spacers to improve isoelectric focusing resolving power: implications for use in two-dimensional electrophoresis.

Presented here is a straightforward and inexpensive method for expanding isoelectric focusing pH gradients relative to the gradients that are formed by commercially available narrow range ampholytes. This method requires no special equipment or techniques and is applicable to isoelectric focusing in acrylamide gels, in Sephadex, and in agarose. The utility of separators in improving the resolving power of two-dimensional polyacrylamide gel electrophoresis is demonstrated using proteins from the exocytotic trichocyst organelle of Paramecium tetraurelia. The mode of action of separators is briefly described.

Assessment by sedimentation equilibrium analysis of a heterologous macromolecular interaction in the presence of self-association: interaction of S5 with S8.

The proteins S5 and S8 from the Escherichia coli 30S ribosomal subunit have been examined by sedimentation equilibrium methods for behavior in solution as isolated components and in mixtures. The means of resolving two simultaneous associations in this system is discussed, and the energy of association of S5 and S8 is reported. It was found that protein S5 from the MRE 600 strain tends to self-associate weakly at 4 degree C in a manner that can be described as an isodesmic self-association with an association constant and corresponding standard Gibbs free energy equal to (7.7 +/- 0.7) X 10(3) M-1 and -4.9 +/- 0.1 kcal/mol, respectively. Protein S8 was found to have a molecular weight of 15800 and was monomeric in a pure state. Mixtures of S5 and S8 clearly demonstrated the presence of an S5-S8 complex in addition to the self-association of S5. The equilibrium constant of association for the formation of a simple S5-S8 complex at 4 degree C and the corresponding standard Gibbs free energy were found to be (5.5 +/- 1.0) X 10(4) M-1 and -6.0 +/- 0.1 kcal/mol, respectively.