Format

Send to

Choose Destination
Protein Sci. 1998 Jun;7(6):1423-30.

Electrospray-ionization mass spectrometry of intact intrinsic membrane proteins.

Author information

1
Center for Molecular and Medical Sciences Mass Spectrometry, Department of Chemistry & Biochemistry, University of California, Los Angeles 90095-1569, USA. jpw@chem.ucla.edu

Abstract

Membrane proteins drive and mediate many essential cellular processes making them a vital section of the proteome. However, the amphipathic nature of these molecules ensures their detailed structural analysis remains challenging. A versatile procedure for effective electrospray-ionization mass spectrometry (ESI-MS) of intact intrinsic membrane proteins purified using reverse-phase chromatography in aqueous formic acid/isopropanol is presented. The spectra of four examples, bacteriorhodopsin and its apoprotein from Halobacterium and the D1 and D2 reaction-center subunits from spinach thylakoids, achieve mass measurements that are within 0.01% of calculated theoretical values. All of the spectra reveal lesser quantities of other molecular species that can usually be equated with covalently modified subpopulations of these proteins. Our analysis of bovine rhodopsin, the first ESI-MS study of a G-protein coupled receptor, yielded a complex spectrum indicative of extensive molecular heterogeneity. The range of masses measured for the native molecule agrees well with the range calculated based upon variable glycosylation and reveals further heterogeneity arising from other covalent modifications. The technique described represents the most precise way to catalogue membrane proteins and their post-translational modifications. Resolution of the components of protein complexes provides insights into native protein/protein interactions. The apparent retention of structure by bacteriorhodopsin during the analysis raises the potential of obtaining tertiary structure information using more developed ESI-MS experiments.

PMID:
9655347
PMCID:
PMC2144037
DOI:
10.1002/pro.5560070619
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center