Showing papers by "Jose A. Gavira published in 2007"

Structure of the mexicain-E-64 complex and comparison with other cysteine proteases of the papain family.

Abstract: Mexicain is a 23.8 kDa cysteine protease from the tropical plant Jacaratia mexicana. It is isolated as the most abundant product after cation-exchange chromatography of the mix of proteases extracted from the latex of the fruit. The purified enzyme inhibited with E-64 [N-(3-carboxyoxirane-2-carbonyl)-leucyl-amino(4-guanido)butane] was crystallized by sitting-drop vapour diffusion and the structure was solved by molecular replacement at 2.1 A resolution and refined to an R factor of 17.7% (R(free) = 23.8%). The enzyme belongs to the alpha+beta class of proteins and the structure shows the typical papain-like fold composed of two domains, the alpha-helix-rich (L) domain and the beta-barrel-like (R) domain, separated by a groove containing the active site formed by residues Cys25 and His159, one from each domain. The four monomers in the asymmetric unit show one E-64 molecule covalently bound to Cys25 in the active site and differences have been found in the placement of E-64 in each monomer.

New techniques for membrane protein crystallization tested on photosystem II core complex of Pisum sativum

Abstract: The crystallization of a given protein is a hard task being even more complicated when the protein shows a hydrophobic behavior. In the case of photosynthetic proteins, the difficulty of the experiments increased due to the high light sensitivity. Aqueous solutions of photosystem II core complex (OEC PSII) of Pisum sativum were screened for crystallization conditions using standard crystallization methods. Crystal improvement was achieved by counter-diffusion technique in single capillaries of 0.2 mm inner diameter with a three-layer configuration. The use of this advanced crystallization technique—for the first time applied to the crystallization of membrane proteins—improves the reproducibility of the experiments allowing the initial crystal characterization, and facilitates the manipulation under light protection.

Crystallization by capillary counter-diffusion and structure determination of the N114A mutant of the SH3 domain of Abl tyrosine kinase complexed with a high-affinity peptide ligand.

Abstract: The recognition of proline-rich ligands by SH3 domains is part of the process leading to diseases such as cancer or AIDS. Understanding the molecular determinants of the binding affinity and specificity of these interactions is crucial for the development of potent inhibitors with therapeutic potential. In this study, the crystallographic structure of the N114A mutant of the SH3 domain of the Abelson leukaemia virus tyrosine kinase complexed with a high-affinity peptide is presented. The crystallization was carried out using the capillary counter-diffusion technique, which facilitates the screening, manipulation and transport of the crystals and allows the collection of X-ray data directly from the capillary in which the crystals were grown. The crystals of the N114A mutant belong to the orthorhombic P2(1)2(1)2(1) space group, with unit-cell parameters a = 48.2, b = 50.1, c = 56.4 A. The quality of the diffraction data set has allowed the structure of the complex to be determined at a resolution limit of 1.75 A.