Crystallization and preliminary X-ray studies of two isolectins from the seeds of Lathyrus ochrus

Abstract

Two isolectins from the seeds of Lathyrus ochrus, LOL I and LOL II, which specifically bind N-acetyllactosamine, have been crystallized using the hanging-drop method and the interface diffusion method, respectively. In the case of LOL I, 2-methylpentane-2,4-diol, polyethylene-glycol 400 or ammonium sulphate have been used as precipitating agents. The best crystals of LOL I were grown at room temperature from a solution of 40% ( v v ) methylpentane diol, 50 mM-Hepes at pH 7.5. LOL II crystals have been grown at room temperature from a solution of 32% ( v v ) methylpentane diol, 50 m m-2( N-morpholino)-ethanesulphonic acid at pH 5.5. X-ray examination of the LOL I and LOL II crystals shows that both are monoclinic, space group P2 1. Their cell dimensions are: LOL I, a = 56.4 A ̊ , b = 138.8 A ̊ , c = 62.9 A ̊ , β = 91° ; and LOL II, a = 54.8 A ̊ , b = 71.4 A ̊ , c = 105.5 A ̊ , β = 105 ° . Density measurements of the crystals of LOL I indicate that there are two molecules per asymetric unit ( V m = 2.07 A ̊ 3/dalton ). LOL I crystals diffract strongly up to at least 1.8 resolution. Putative crystals of complexes of LOL I with various glycosides were obtained through co-crystallization under the conditions used for the native protein.