[ccp4bb]: Cleaved site in protein structure

[Jinkwang]

Hi all,   Routine MR solution of a mutant structure was an easy task until I found a clear cleavage within the polypeptide chain. This cleavage is reproducible only in crystal structure, and biochemical studies such as SDS-PAGE, N-terminal sequencing or Mass spectra never indicate any cleavage in the chain.   The protein has about 700 amino acids, divided into alpha (200 a.a) and beta (500) chains. The cleavage is found at 28-29 of the beta chain in the crystal. Wondering whether this could occur only in crystal states, the crystals were dissolved, but the biochemical studies did not show any cleavage, but crystal structure once again shows.   Any comments are highly appreciated.   Regards,   Jin Kwang