Abstract
This report describes an analysis of the red blood cell proteome by ion trap tandem mass spectrometry in line with liquid chromatography. Mature red blood cells lack all internal cell structures and consist of cytoplasm within a plasma membrane envelope. To maximize outcome, total red blood cell protein was divided into two fractions of membrane-associated proteins and cytoplasmic proteins. Both fractions were divided into subfractions, and proteins were identified in each fraction separately through tryptic digestion. Membrane protein digests were collected from externally exposed proteins, internally exposed proteins, "spectrin extract" mainly consisting of membrane skeleton proteins, and membrane proteins minus spectrin extract. Cytoplasmic proteins were divided into 21 fractions based on molecular mass by size exclusion chromatography. The tryptic peptides were separated by reverse-phase high-performance liquid chromatography and identified by ion trap tandem mass spectrometry. A total of 181 unique protein sequences were identified: 91 in the membrane fractions and 91 in the cytoplasmic fractions. Glyceraldehyde-3-phosphate dehydrogenase was identified with high sequence coverage in both membrane and cytoplasmic fractions. Identified proteins include membrane skeletal proteins, metabolic enzymes, transporters and channel proteins, adhesion proteins, hemoglobins, cellular defense proteins, proteins of the ubiquitin-proteasome system, G-proteins of the Ras family, kinases, chaperone proteins, proteases, translation initiation factors, and others. In addition to the known proteins, there were 43 proteins whose identification was not determined.
Highlights
This report describes an analysis of the red blood cell proteome by ion trap tandem mass spectrometry in line with liquid chromatography
A peptide coeluted from the high-performance liquid chromatography (HPLC) column with more abundant peptides or a high number of other peptides may not be detected even if its absolute concentration in an eluate is within the sensitivity of the mass spectrometer
The human red blood cell (RBC) provides an ideal model for proteomic analysis because it combines simplicity with physiologic significance
Summary
This report describes an analysis of the red blood cell proteome by ion trap tandem mass spectrometry in line with liquid chromatography. The abbreviations used are: RBC, red blood cell; HPLC, highperformance liquid chromatography; IOV, inside out vesicles; MS, mass spectrometry; LC/MS/MS, liquid chromatography in line with tandem mass spectrometry; MALDI-TOF, matrix-assisted laser desorption/ionization time-of-flight; PBS, phosphate-buffered saline. This kind of approach is a necessary first step in understanding how the RBC proteome becomes altered in various hematologic disorders With this goal in mind, we utilized ion trap tandem MS to analyze the entire human erythrocyte proteome (plasma membrane and cytoplasmic proteins). We were able to identify the proteins but to categorize most of them according to function
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