NMR analysis on the sialic acid-binding mechanism of an R-type lectin mutant by natural evolution-mimicry.

A sialic acid-binding lectin (SRC) was created from the C-terminal domain of an R-type N-acetyl lactosamine-binding lectin (EW29Ch) by natural evolution-mimicry. Here, we clarified its sialic acid-binding mechanism using NMR spectroscopy. The NMR analysis showed differences between conformations of the 6'-sialyllactose-bound SRC in the solution state and that in the crystal state, and differences between the internal motion of the loop region in subdomain γ in SRC and that of the corresponding region in EW29Ch. The NMR analysis thus provided useful information to explain the manner of binding to 6'-sialyllactose in solution, which the previous X-ray crystal structure analysis lacked.