Lectins carbohydrate crystal structures

A listing of the X-ray crystal structure (arranged in chronological order) of plant lectins is presented in Table 2 commencing with the structure of concanavalin A at 3 A resolution [38,39]. Interestingly, it was not until 1989 that a definitive high resolution X-ray crystal structure of the concanavalin A-methyl a-D-mannopyranoside complex was elucidated [40], and the most recently reported is that of peanut agglutinin [41]. Reviews on carbohydrate-protein interactions are also worthy of note [42-45]. 

T. Fujii, M. Hayashida, M. Hamasu, M. Ishiguru, and Y. Hato, Structures of two lectins from the roots of pokeweed (Phytolacca americana), Acta Crystallogr. D, 60 (2004) 665-673 M. Hayashida, T. Fujii, M. Hamasu, M. Ishiguro, and Y. Hata, Similarity between protein-protein and protein-carbohydrate interactions, revealed by two crystal structures of lectins from the roots of pokeweed, /. Mol. Biol., 334 (2003) 551-565. 

The crystal structures of two large sialidases have been determined the 83 kDa Vibrio cholerae sialidase [17] and the 68 kDa M. viridifaciens sialidase [19], both shown in Figure 2. The V. cholerae enzyme revealed a central catalytic P-propeller domain, flanked by two additional domains with similar topologies, resembling that of the lectins. The first lectin domain is at the N-terminus, and the second is inserted between the second and third sheets of the P-propeller. The lectin domains bind on as yet unidentified carbohydrate, but their structure suggests a role for these domains in the small intestine where the secreted sialidase may need to grasp the cell surface to perform its catalytic function without being swept away. 

In recent years substantial progress has been made in achieving an understanding of the structural attributes that contribute to the carbohydrate binding properties of these proteins. Indeed the crystal structures of approximately 20 plant lectins have... 

A vast amount of information is presently available on the structures of plant lectins, including the complete amino acid sequences of many of these proteins and the crystal structures of almost 20 different lectins, many in complex with their carbohydrate ligands. Several excellent reviews on these structures have appeared within the past two years [4, 25, 26] to which the reader is referred for more detailed considerations than can be provided in the present chapter. In general, the structures of lectins obtained from species within the same phylogenetic class of plants are quite similar to one another but differ markedly from the structures of lectins from plants of other classes. The largest amount of information is available on the lectins from the seeds of legumes which can comprise up to 10% of the total seed protein. The... 

Calcium one is considered to be involved in maintaining lectin structure while calcium two coordinates directly with carbohydrate, and calcium three is believed to be an artifact of crystallization [20]. 

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