JMSSJ On-line, Vol. 46 (1998) No. 5, pp. 429-432
Biological Significance of the Precise Mass Measurement of Proteins
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    Yoshinao WADA*

    * Department of Molecular Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health (840 Murodo-cho, Izumi, Osaka 594-1101, Japan)

Achievement of the unit mass accuracy in the molecular mass determination of proteins has been stressed. Single mass change of proteins is caused by single amino acid substitutions including Glu/Lys, Asn/Leu, Asn/Ile, Asp/Asn, and Glu/Gln, of which four mutations except for Asn/Leu are produced by single nucleotide changes. In the case of Hemoglobin Hoshida, a substitution of Asn for Asp was found in a peptide of 2056.9 Da with a decrease of single mass unit. In a structural study of the transferrin isoform which is characteristic of carbohydrate-deficient glycoprotein syndrome and missing asparagine-linked oligosaccharides, assignment of Asn but not Asp for the residue that should be glycosylated was necessary for delineating the molecular pathogenesis of this disorder. However, as demonstrated in β2-microglobulin, proteins are often partially deamidated during sample preparation or in vivo. This may compromise the biological significance of the precise mass measurement of proteins.

Key words: Mutation, Unit mass, Electrospray ionization, Deamidation, Protein

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