Complete Amino Acid Sequence of the Protease Inhibitor BWI-4a from Buckwheat Seeds

M. A. Belozersky^1*, Y. E. Dunaevsky¹, A. Kh. Musolyamov², and T. A. Egorov²

¹Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-3181; E-mail: mbeloz@genebee.msu.su

²Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow, 117871 Russia; fax: (095) 330-7301; E-mail: ego@ibch.siobc.ras.ru

^* To whom correspondence should be addressed.

Received April 26, 2000; Revision received July 1, 2000

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The complete amino acid sequence of the protease inhibitor BWI-4a from buckwheat (Fagopyrum esculentum Moench) seeds has been established by automated Edman degradation in combination with MALDI-TOF mass spectrometry. The inhibitor molecule consists of 67 amino acid residues with a single disulfide bond. Its N-terminus is blocked by a pyroglutamic acid residue. The reactive site of the inhibitor contains an Arg43-Asp44 bond. Mass spectrometry revealed that inhibitor BWI-4a is present in buckwheat seeds in two isoforms differing by a single amino acid substitution of Gly40 for Ala40. Analysis of the amino acid sequence of the BWI-4a inhibitor indicates that this inhibitor is a member of the potato proteinase inhibitor I family.

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KEY WORDS: amino acid sequence, buckwheat seeds, mass spectrometry,microheterogeneity, protease inhibitors

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