title: The thermal stability of the external invertase isoforms from Saccharomyces cerevisiae correlates with the surface charge density.
abstract: Understanding the effect of surface charge on the stability of proteins is one prerequisite for "tailoring" proteins with increased thermal stability. Here, we investigated the origin of the altered thermal stability observed between the four recently isolated isoforms (EINV1-EINV4) of external invertase. External invertase from yeast Saccharomyces cerevisiae, a homodimeric glycoprotein, represents a widely used model for studying the influence of the glyco component on protein stability. The stability of the four isoforms of invertase decreases from EINV1 to EINV4, which is accompanied by an increase in negative surface charge density. Mass spectrometry analysis revealed that the isoforms share identical protein parts indicating that the differences in stability are the result of post-translational modifications. (31)P NMR analysis revealed that the isoforms contain negatively charged phosphate groups in diester and monoester forms attached to the glycan part. The total amount of phosphate bound to the polymannan component varies between the different isoforms. These results, together with the analysis of the amount of polymannan components, show that negative surface charge density does not entirely depend on the amount of phosphate but rather on its distribution. This suggests that charged groups bound to the glyco-component of a protein can influence the stability of glycoproteins.
authors: Institute for Chemistry, Technology and Metallurgy, Department of Chemistry, University of Belgrade, Studentski trg 12 - 16, 11000 Belgrade, Serbia. uros@chem.bg.ac.rs
authors: Uroš
authors: U
authors: Andjelković
authors: Stephan
authors: S
authors: Theisgen
authors: Holger A
authors: HA
authors: Scheidt
authors: Marijana
authors: M
authors: Petković
authors: Daniel
authors: D
authors: Huster
authors: Zoran
authors: Z
authors: Vujčić
mesh_terms: D004795:Enzyme Stability; D006023:Glycoproteins / Q000378:metabolism; D006031:Glycosylation; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000378:metabolism; D013058:Mass Spectrometry; D019906:Nuclear Magnetic Resonance, Biomolecular; D055503:Protein Multimerization; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D055672:Static Electricity; D013816:Thermodynamics; D043324:beta-Fructofuranosidase / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D007527:Isoenzymes; D029701:Saccharomyces cerevisiae Proteins; D043324:beta-Fructofuranosidase