Proteomics on full-length membrane proteins using mass spectrometry

A general technique has been developed that allows rapid mass spectrometric analysis of full-length membrane proteins [Whitelegge, J. P., le Coutre, J ., et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 10695-10698], Using in-l ine HPLC electrospray ionization mass spectrometry (LC-MS), different nativ e and recombinant bacterial membrane proteins of up to 61 kDa are character ized. Mass spectrometric data of four entirely different membrane proteins from three bacterial organisms, two transporters, a channel, and a porin pr otein are presented. In addition to determination of the molecular mass wit h an accuracy of +/-0.01%, the technique monitors alkylation or oxidation o f single Cys residues and errors in deduced amino acid sequences. Finally, using in-line LC-MS, unknown proteins can be identified from solubilized Es cherichia coli membranes without prior purification.