Sue Cutfield

Low resolution crystal structure of hagfish insulin

Abstract Insulin from the Atlantic hagfish, Myxine glutinosa, crystallizes in space group P41212 with a monomer in the asymmetric unit. The application of the Rossmann & Blow (1962) rotation function, utilizing the known 2-zinc pig insulin crystal structure, has established the existence of an insulin dimer containing a crystallographic 2-fold axis. The position of the hagfish insulin molecule in the unit cell has been determined and a set of calculated phases derived. These are compared to phases found from isomorphous replacement studies. A 6 A resolution electron density map has been calculated which shows the A and B chains are folded in a similar way to pig insulin and that the monomers are similarly organized into dimers.

Structure of Secreted Aspartic Proteinases from Candida

Pathogens of the genus Candida can cause life threatening infections in immunocompromised patients. The three–dimensional structures of two closely related secreted aspartic proteinases from C. albicans complexed with a potent (Ki=0.17 nM) inhibitor, and an analogous enzyme from C. tropicalis reveal variations on the classical aspartic proteinase theme that dramatically alter the specificity of this class of enzymes. The novel fungal proteases present: i) an 8 residue insertion near the first disulfide (Cys45–Cys50, pepsin numbering) that results in a broad flap extending towards the active site; ii) a seven residue deletion replacing helix hN2 (Serll0–Tyrll4), which enlarges the S3 pocket; iii) a short polar connection between the two rigid body domains that alters their relative orientation and provides certain specificity; and iv) an ordered 12 residue addition at the car–boxy terminus. The same inhibitor (A–70450) binds in an extended conformation in the two variants of C albicans protease, and presents a branched structure at the P3 position. However, the conformation of the terminal methylpiperazine ring is different in the two crystals structures. The implications of these findings for the design of potent antifungal agents are discussed.

Crystallization of the exo(1,3)-β-glucanase from Candida albicans

An exoglucanase, with specificity for beta (1,3) linkages, from the cell wall of Candida albicans has been crystallized by the hanging drop method in the presence of polyethylene glycol 8000. The crystals, which diffract to better than 1.9 A resolution, belong to the orthorhombic space group P212121 with cell constants a = 60.2 A, b = 65.2 A, c = 96.5 A and with one molecule in the asymmetric unit.