title: Proteins contribute insignificantly to the intrinsic buffering capacity of yeast cytoplasm.
abstract: Intracellular pH is maintained by a combination of the passive buffering of cytoplasmic dissociable compounds and several active systems. Over the years, a large portion of and possibly most of the cell's intrinsic (i.e., passive non-bicarbonate) buffering effect was attributed to proteins, both in higher organisms and in yeast. This attribution was not surprising, given that the concentration of proteins with multiple protonable/deprotonable groups in the cell exceeds the concentration of free protons by a few orders of magnitude. Using data from both high-throughput experiments and in vitro laboratory experiments, we tested this concept. We assessed the buffering capacity of the yeast proteome using protein abundance data and compared it to our own titration of yeast cytoplasm. We showed that the protein contribution is less than 1% of the total intracellular buffering capacity. As confirmed with NMR measurements, inorganic phosphates play a crucial role in the process. These findings also shed a new light on the role of proteomes in maintaining intracellular pH. The contribution of proteins to the intrinsic buffering capacity is negligible, and proteins might act only as a recipient of signals for changes in pH.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Poznanski
authors.forename: Pawel
authors.initials: P
authors.lastname: Szczesny
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Ruszczyńska
authors.forename: Piotr
authors.initials: P
authors.lastname: Zielenkiewicz
authors.forename: Leszek
authors.initials: L
authors.lastname: Paczek
mesh_terms: D002021:Buffers; D003593:Cytoplasm / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D020543:Proteome / Q000737:chemistry; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*
chemical_list: D002021:Buffers; D020543:Proteome; D011522:Protons; D029701:Saccharomyces cerevisiae Proteins