MATRIX-ASSISTED-LASER-DESORPTION IONIZATION AND ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY ANALYSIS OF BLUE COPPER PROTEINS - AZURIN AND MAVICYANIN/

Two copper proteins azurin-1 and azurin-2 were isolated from denitrify ing bacteria Alcaligenes xylosoxidans GIFU1051, and the mass spectrome tric analysis of the proteins were carried out by both matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and electrospr ay ionization (ESI), The mass spectrometric analysis was also carried out with the recombinant zucchini protein mavicyanin, which was obtain ed by expression in Escherichia coli, All the proteins were detected a s positive ions with the copper atom being eliminated. The molecular w eights were determined as 14 017.6 for azurin-1, 13 807.6 for azurin-2 and 11 808.8 for mavicyanin, The observed molecular weight of azurin- 1 agrees within two daltons with that calculated from the amino acid c omposition, Azurin-2 was found to have one different amino acid residu e when compared with the known azurin-2 isolated from A. xylosoxidans NCIB11015. The measured molecular weight for the recombinant mavicyani n agrees within two daltons with that of calculated from the amino aci d composition of the native protein; therefore, the recombinant mavicy anin is identical to the native protein. (C) 1998 John Wiley & Sons, L td.