STRUCTURE OF HEVEIN, A LECTIN-LIKE FROM HEVEA BRASILIENSIS AT 1.9Å RESOLUTION. Kaliyamoorthy Panneerselvam and Manuel Soriano-García. Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Delegación Coyoacán 04510. México, D.F.

Hevein is a small, single-chain protein of 43 amino acids and rich in cysteine and glycine. Hevein is a lectin-like protein and experimental evidence indicates that this protein is involved in the coagulation of latex by bridging together rubber particles¹. We solved the crystal structure of hevein by means of molecular replacement techniques using the PROTEIN program and refined the structure at 3.0Å resolution². However, the resolution limit of the diffraction data collected could be improved and prompted us to remeasure a new native data-set up to 1.9 Å resolution. The crystals are orthorhombic with space group P2₁2₁2₁ with cell dimensions a= 21.59(2), b= 31.60(3) and c= 51.21(5)Å, V= 34931(1) ų and Z= 4. The three-dimensional structure of hevein has been refined with XPLOR and SHELXL93 programs. A total of 324 protein atoms, 20 ordered water sites and 23 disorder water sites refined to a final R-factor of 0.16 at a resolution of 1.9Å and an average B-value of 15.1Ų, using 73% (2326) of the total possible number of reflections in the range 10 to 1.9 Å with I > 2s(I). The final structure has r.m.s deviations from ideal bond distances and angles of 0.017Å and 2.7^o, respectively. The standard deviation of atomic position estimated by Luzzzati plot was 0.15Å. The protein comprised of four-stranded ß-sheet, five turns and a short a-helix located at the C-terminal, all of these is required to accomplish the hevein-lectin like fold. The final structure of hevein in the solid state displays a folding similar to one determined by NMR techniques and also to that of domain C of wheat germ agglutinin.

This work was supported by DGAPA, UNAM grant IN201294.

[1]Gidrol, X., et al., (1994). J. Biol. Chem. 269, 9278-9283.

[2]Rodríguez-Romero, A., et al., (1991)FEBS Lett.291,307-309.