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Published on: February 25, 2011
2-D native-PAGE/SDS-PAGE visualization of an oligomer's subunits: application to the analysis of IgG
Leticia Gonzalez1, Juan J Bustamante, Edwin J Barea-Rodriguez
1Department of Integrative Physiology, The University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, USA.
Insights
This study introduces a sensitive 2-D native-PAGE/SDS-PAGE method for detecting protein oligomer subunits. The optimal approach combines Coomassie staining with permanganate silver staining for high-sensitivity subunit visualization.
Area of Science:
- Biochemistry
- Proteomics
- Analytical Chemistry
Background:
- Protein oligomers are complex assemblies crucial for biological function.
- Accurate detection of subunit composition is vital for understanding protein structure-function relationships.
- Existing methods often lack the sensitivity required for low-abundance oligomeric proteins.
Purpose of the Study:
- To develop and validate a highly sensitive two-dimensional gel electrophoresis method for identifying protein oligomer subunits.
- To compare the sensitivity of various staining techniques in a 2-D native-PAGE/SDS-PAGE system.
- To establish an optimal staining protocol for visualizing protein subunits from oligomeric assemblies.
Main Methods:
- Utilized a 2-D native-PAGE followed by SDS-PAGE to separate protein oligomers and their subunits.
- Investigated multiple staining methods including silver stains, Coomassie stains, metal ion reverse-staining, and fluorescent staining.
- Excised protein bands from the native gel, re-electrophoresed on SDS-PAGE, and visualized subunits.
Main Results:
- The combination of Coomassie R-250 staining in the first dimension and permanganate silver staining in the second dimension achieved the highest sensitivity (2-3 pmol).
- Coomassie G-250 and native fast silver staining also enabled subunit detection, albeit at slightly lower sensitivities (3 pmol and 13 pmol, respectively).
- Other staining methods (ammoniacal silver, copper, zinc, SYPRO Ruby) in the first dimension were less effective due to protein streaking or immobilization.
Conclusions:
- A 2-D native-PAGE/SDS-PAGE approach is effective for analyzing protein oligomer subunit composition.
- Coomassie staining followed by permanganate silver staining offers the most sensitive method for visualizing subunits from oligomeric assemblies.
- This optimized method significantly enhances the ability to detect and characterize protein subunits at low picomole levels.
Abstract:
A 2-D native-PAGE/SDS-PAGE method for detecting the subunit components of protein oligomers at low picomole sensitivity is presented. IgG was electrophoresed in a native acidic polyacrylamide gel in amounts ranging from 51 pmol to 60 fmol. Silver-staining (native fast silver stain, ammoniacal silver stain, permanganate silver stain), Coomassie-staining (R-250, G-250), metal ion-reverse-staining (zinc, copper), and fluorescent chromophore-staining (SYPRO Ruby) methods were used to visualize the IgG oligomers. The protein zones were then excised, separated by SDS-PAGE, and subunits visualized with a permanganate silver stain. The Coomassie R-250/permanganate silver-staining combination detected IgG subunits using 2 pmol of sample. Coomassie G-250 and native fast silver staining in the first-dimensional gel produced detectable subunits in the second-dimensional separation at 3 and 13 pmol, respectively. Staining with silver (ammoniacal, permanganate), copper, zinc, or SYPRO Ruby in the first-dimensional gel did not produce discernible subunits in the second-dimensional gels due to protein streaking or protein immobilization in the native gel. When using a 2-D native-PAGE/SDS-PAGE system, Coomassie staining of the first-dimensional native gel combined with permanganate silver staining of the second-dimensional denaturing gel provides the most sensitive method (2-3 pmol) for visualizing constituent subunits from their oligomeric assemblies.
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