title: Increase in the susceptibility of hemoglobin to proteases upon treatment with p-mercuribenzoate.
abstract: Native human oxyhemoglobin, which has a rigid conformation resistant to proteases such as trypsin and subtilisin, could be hydrolyzed by these proteases at pH 7.0 after treatment with p-chloromercuribenzoate. The digestion curve of hemoglobin as a function of concentration of the mercurial was essentially parallel to the titration curve of hemoglobin with the mercurial, indicating that a relationship exists between susceptibility to proteases and modification of thiol groups of the protein. On the other hand, when myoglobin was used as a substrate, the degree of proteolysis did not increase after treatment with the mercurial. Circular dichroism measurements and gel-filtration experiments showed that the observed increase in susceptibility of hemoglobin to proteases was not due to a conformational change involving unfolding of alpha-helical structure, but was due to the dissociation of the tetrameric hemoglobin molecule into dimer and monomer after treatment with the mercurial.
mesh_terms: D002364:Caseins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008626:Mercuribenzoates / Q000494:pharmacology*; D008706:Methemoglobin / Q000378:metabolism; D008970:Molecular Weight; D009211:Myoglobin / Q000378:metabolism; D010108:Oxyhemoglobins / Q000378:metabolism*; D011487:Protein Conformation; D013381:Subtilisins / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000032:analysis; D014357:Trypsin / Q000378:metabolism*; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000494:pharmacology
chemical_list: D002364:Caseins; D008626:Mercuribenzoates; D009211:Myoglobin; D010108:Oxyhemoglobins; D013438:Sulfhydryl Compounds; D008706:Methemoglobin; D014360:Trypsin Inhibitor, Kunitz Soybean; D013381:Subtilisins; D014357:Trypsin