TitleMineral Surfaces as Agents of Environmental Proteolysis: Mechanisms and Controls.
Publication TypeJournal Article
Year of Publication2019
AuthorsChacon SS, Reardon PN, Burgess CJ, Purvine S, Chu RK, Clauss TR, Walter E, Myrold DD, Washton N, Kleber M
JournalEnviron Sci Technol
Volume53
Issue6
Pagination3018-3026
Date Published2019 03 19
ISSN1520-5851
KeywordsKaolin, Minerals, Oxidation-Reduction, Proteolysis, Soil
Abstract

We investigated the extent to which contact with mineral surfaces affected the molecular integrity of a model protein, with an emphasis on identifying the mechanisms (hydrolysis, oxidation) and conditions leading to protein alteration. To this end, we studied the ability of four mineral surface archetypes (negatively charged, positively charged, neutral, redox-active) to abiotically fragment a well-characterized protein (GB1) as a function of pH and contact time. GB1 was exposed to the soil minerals montmorillonite, goethite, kaolinite, and birnessite at pH 5 and pH 7 for 1, 8, 24, and 168 h and the supernatant was screened for peptide fragments using Tandem Mass Spectrometry. To distinguish between products of oxidative and hydrolytic cleavage, we combined results from the SEQUEST algorithm, which identifies protein fragments that were cleaved hydrolytically, with the output of a deconvolution algorithm (DECON-Routine) designed to identify oxidation fragments. All four minerals were able to induce protein cleavage. Manganese oxide was effective at both hydrolytic and oxidative cleavage. The fact that phyllosilicates-which are not redox active-induced oxidative cleavage indicates that surfaces acted as catalysts and not as reactants. Our results extend previous observations of proteolytic capabilities in soil minerals to the groups of phyllosilicates and Fe-oxides. We identified structural regions of the protein with particularly high susceptibility to cleavage (loops and β strands) as well as regions that were entirely unaffected (α helix).

DOI10.1021/acs.est.8b05583
Alternate JournalEnviron. Sci. Technol.
PubMed ID30767514