Identification of Missing Proteins in the Phosphoproteome of Kidney Cancer

Identifying missing proteins (MPs)
has been one of the critical
missions of the Chromosome-Centric Human Proteome Project (C-HPP).
Since 2012, over 30 research teams from 17 countries have been trying
to search adequate and accurate evidence of MPs through various biochemical
strategies. MPs mainly fall into the following classes: (1) low-molecular-weight
(LMW) proteins, (2) membrane proteins, (3) proteins that contained
various post-translational modifications (PTMs), (4) nucleic acid-associated
proteins, (5) low abundance, and (6) unexpressed genes. In this study,
kidney cancer and adjacent tissues were used for phosphoproteomics
research, and 8962 proteins were identified, including 6415 phosphoproteins,
and 44 728 phosphosites, of which 10 266 were unreported
previously. In total, 75 candidate detections were found, including
45 phoshoproteins. GO analysis for these 75 candidate detections revealed
that these proteins mainly clustered as membrane proteins and took
part in nephron and kidney development. After rigorous screening and
manual check, 9 of them were verified with the synthesized peptides.
Finally, only one missing protein was confirmed. All mass spectrometry
data from this study have been deposited in the PRIDE with identifier
PXD006482.