Beta-endorphin-containing proteins in the human pituitary.
Two new proopiomelanocortin (POMC)-derived beta-endorphin (BE)-containing proteins were detected in the human pituitary, using HPLC, trypsin digestion, and a high sensitivity search with liquid secondary ion mass spectrometry (LSIMS) for the protonated molecule ion, (M + H)+, of tryptic peptides that are unique to BE. Proteins were extracted from pituitary tissues and were purified by solid phase extraction (SPE) chromatography and RP-HPLC. Each HPLC fraction was treated with trypsin, and each unseparated peptide mixture was analyzed by LSIMS to detect the two selected marker peptides (BE 20-24 and BE 10-19) that have excellent LSIMS desorption-ionization properties. The detection of both of those peptides indicated the presence of BE-containing proteins in two HPLC fractions (number 47 and 51). Tandem MS determined the amino acid sequence of the marker peptide BE 20-24 (NAIIK), and those sequence data optimized the specificity of the method. The two new BE-containing proteins derive from the C-terminal region of POMC, and were minor components in the two HPLC fractions. The major component in fraction 51 derived from the vasopressin-neurophysin 2-copeptin precursor.
Yan
L
L
Charles B. Stout Neuroscience Mass Spectrometry Laboratory, Memphis, TN, USA.
Zhu
X
X
Tseng
J L
JL
Desiderio
D M
DM
D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry*; D011333:Pro-Opiomelanocortin / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D012680:Sensitivity and Specificity; D001615:beta-Endorphin / Q000032:analysis*
D011506:Proteins; D001615:beta-Endorphin; D011333:Pro-Opiomelanocortin