Exploring the phosphoproteome profiles during Xenopus egg activation by calcium stimulation using a fully automated phosphopeptide purification system

To explore the phosphoproteome profiles during Xenopus egg activation by Ca2+-stimulation, an automated phosphopeptide purification system involving a titania column was improved by introducing 4-step elution with phosphate buffers. The number of detected phosphopeptides in the tryptic digest of a Xenopus egg cytosol fraction on mass spectrometry (MS) was increased 1.5-fold and the percentage of multiply phosphorylated peptides increased from 17 to 24% with introduction of the 4-step elution method. Phosphopeptides were purified by the improved method from tryptic digests of cytosol fractions of Xenopus eggs without and with a Ca2+-stimulus, and then, analysed by MS. One thousand three hundred and seventy-five and 994 phosphopeptides were reproducibly detected on duplicate MS, respectively. They included 818 and 437 phosphopeptides specific to each digest, respectively. A method involving isobaric tags for relative and absolute quantitation (iTRAQ) was also applied to compare the phosphorylation levels in Xenopus eggs without and with a Ca2+-stimulus, the ratios for 112 phosphopeptides in tryptic digests of these egg cytosol fractions being obtained. It was suggested from all the results that the phosphorylation sites and levels change during Xenopus egg activation for many known and unknown sites on structural proteins, signalling related proteins, cell cycle-related proteins and others.

Source: Journal of Biochemistry - March 20, 2016 Category: Biochemistry Authors: Kanno, T., Furukawa, K., Horigome, T. Tags: Regular Papers Source Type: research