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1. Subunit Composition of a Protein A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein gives three bands with molecular masses of 180, 160, and 60 kDa. When electrophoresis is carried out in the presence of SDS and dithiothreitol, three bands are again formed, this time with molecular massesof 160, 90, and 60 kDa. Determine the subunit composition of the protein.

1. Subunit Composition of a Protein A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein gives three bands with molecular masses of 180, 160, and 60 kDa. When electrophoresis is carried out in the presence of SDS and dithiothreitol, three bands are again formed, this time with molecular massesof 160, 90, and 60 kDa. Determine the subunit composition of the protein.

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
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***not graded, just a practice problem I do not understand. Thank you so much!
### Subunit Composition of a Protein A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein yields three bands with molecular masses of 180, 160, and 60 kDa. When electrophoresis is conducted in the presence of both SDS and dithiothreitol, three bands are again formed, this time with molecular masses of 160, 90, and 60 kDa. **Determine the subunit composition of the protein.** **Explanation:** The data provides information on the molecular masses of the protein subunits under different conditions: - **Initial protein mass (by gel filtration):** 400 kDa - **SDS only (denaturing, no reducing):** 180 kDa, 160 kDa, 60 kDa - **SDS and dithiothreitol (denaturing and reducing):** 160 kDa, 90 kDa, 60 kDa In gel electrophoresis with SDS, proteins are denatured and separated based on mass. Adding dithiothreitol breaks disulfide bonds, potentially revealing smaller subunits. **Graph/Diagram Explanation:** Although there is no graph or diagram provided in the initial prompt, the given molecular masses can be visualized in a gel electrophoresis setup where each lane represents a different condition (SDS only and SDS with dithiothreitol). Here's a conceptual explanation: 1. **Lane 1 (SDS only):** - Bands: 180 kDa, 160 kDa, 60 kDa 2. **Lane 2 (SDS and dithiothreitol):** - Bands: 160 kDa, 90 kDa, 60 kDa From this, you can infer the following about the protein's subunits: - The 160 kDa band observed in both conditions indicates a subunit that does not have disulfide bonds with other subunits. - The 180 kDa subunit in SDS only splits into 90 kDa and possibly other subunits when reduced, suggesting it may consist of 90 kDa subunits linked by disulfide bonds (180 = 90 + 90). - The 60 kDa band remains unaffected by reducing conditions, indicating no intra-subunit disulfide bonds.
Transcribed Image Text:### Subunit Composition of a Protein A protein has a molecular mass of 400 kDa when measured by gel filtration. When subjected to gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), the protein yields three bands with molecular masses of 180, 160, and 60 kDa. When electrophoresis is conducted in the presence of both SDS and dithiothreitol, three bands are again formed, this time with molecular masses of 160, 90, and 60 kDa. **Determine the subunit composition of the protein.** **Explanation:** The data provides information on the molecular masses of the protein subunits under different conditions: - **Initial protein mass (by gel filtration):** 400 kDa - **SDS only (denaturing, no reducing):** 180 kDa, 160 kDa, 60 kDa - **SDS and dithiothreitol (denaturing and reducing):** 160 kDa, 90 kDa, 60 kDa In gel electrophoresis with SDS, proteins are denatured and separated based on mass. Adding dithiothreitol breaks disulfide bonds, potentially revealing smaller subunits. **Graph/Diagram Explanation:** Although there is no graph or diagram provided in the initial prompt, the given molecular masses can be visualized in a gel electrophoresis setup where each lane represents a different condition (SDS only and SDS with dithiothreitol). Here's a conceptual explanation: 1. **Lane 1 (SDS only):** - Bands: 180 kDa, 160 kDa, 60 kDa 2. **Lane 2 (SDS and dithiothreitol):** - Bands: 160 kDa, 90 kDa, 60 kDa From this, you can infer the following about the protein's subunits: - The 160 kDa band observed in both conditions indicates a subunit that does not have disulfide bonds with other subunits. - The 180 kDa subunit in SDS only splits into 90 kDa and possibly other subunits when reduced, suggesting it may consist of 90 kDa subunits linked by disulfide bonds (180 = 90 + 90). - The 60 kDa band remains unaffected by reducing conditions, indicating no intra-subunit disulfide bonds.
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