Cell surface proteins of Candida albicans: Preparation of extracts and improved detection of proteins

We have reexamined the detection of the components in a β‐mercaptoethanol and ammonium carbonate buffer extract of surface proteins of Candida albicans and the effects of postextraction manipulation of the extract on recovery of extract components. Following sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), preferential staining of some moieties was observed when bands detected by a commercial silver staining method or a Coomassie Brilliant Blue (CBB) staining method were compared. Additional protein bands that were either not detected or poorly detected by a single method alone were readily observed by a combined silver‐CBB staining method. This method also detected alterations in the profile of extracted proteins from organisms grown in the presence of galactose or hemoglobin rather than glucose. Two‐dimensional electrophoresis (2‐DE) gel analysis by double stain showed better detection of several acidic and basic protein spots. Less than 10% of the extract as determined by a dye‐binding assay was lost following either or both lyophilization and dialysis. These manipulations of the extract did not change the protein profile following SDS‐PAGE as determined by the combined staining or Western blot analysis of a 70 kDa protein. These observations suggest that soluble cell wall proteins are not unusually sensitive to procedures routinely used in protein purification. In addition, these studies suggest that a modified staining method that combines both silver stain and CBB stain provides improved detection of cell wall proteins compared to either method alone.