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Cloning and characterization of a second member of the mouse mdr gene family
1Department of Biochemistry, Faculty of Medicine, McGill University, Montreal, Quebec, Canada.
Abstract:
The mammalian mdr gene family comprises a small number of closely related genes. Previously, we have shown that one member, mdr1, has the capacity to convey multidrug resistance to drug-sensitive recipient cells in a gene transfer protocol. However, the functional characteristics of other members of this gene family have not been examined. In this report, we characterize a second member of the mdr gene family which we designated mdr2. We determined the nucleotide sequence corresponding to the complete coding region of this mdr2 transcript. The predicted amino acid sequence of this protein (1,276 amino acids) showed that it is a membrane glycoprotein highly homologous to mdr1 (85%), strongly suggesting that both genes originate from a common ancestor. Regions of divergence between mdr1 and mdr2 proteins are concentrated in two discrete segments of the predicted polypeptides, each approximately 100 residues in length. The mdr2 protein appears to be formed by the duplication of a structural unit which encodes three putative transmembrane loops and a predicted nucleotide-binding fold and is highly homologous to bacterial transport proteins such as hlyB. This strong homology suggests that mdr2 also participates in an energy-dependent membrane transport process. However, the direct relationship, if any, of this new member of the mdr family to multidrug resistance remains to be established. Knowledge of the complete nucleotide sequence and predicted amino acid sequence of the mdr2 gene product will enable the preparation of gene-specific probes and antibodies necessary to study the functional role of this gene in multidrug resistance and normal physiological processes.
Insights
Researchers characterized the mdr2 gene, a new member of the mammalian multidrug resistance (mdr) gene family. The mdr2 protein is a membrane glycoprotein homologous to mdr1, suggesting a shared evolutionary origin and potential role in transport.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The mammalian multidrug resistance (mdr) gene family plays a role in drug resistance.
- The function of mdr gene family members beyond mdr1 is largely uncharacterized.
- mdr1 has been shown to confer multidrug resistance in gene transfer studies.
Purpose of the Study:
- To characterize a newly identified member of the mdr gene family, designated mdr2.
- To determine the nucleotide and amino acid sequence of the mdr2 gene product.
- To investigate the potential functional role of mdr2 in multidrug resistance and physiological processes.
Main Methods:
- Nucleotide sequencing of the mdr2 transcript.
- Prediction of the amino acid sequence and protein structure.
- Homology analysis comparing mdr2 to mdr1 and bacterial transport proteins.
Main Results:
- The complete coding sequence of the mdr2 transcript was determined.
- The predicted mdr2 protein (1,276 amino acids) is a membrane glycoprotein highly homologous (85%) to mdr1.
- Divergence between mdr1 and mdr2 proteins is localized to two distinct segments.
- The mdr2 protein structure suggests a role in energy-dependent membrane transport, similar to bacterial proteins like hlyB.
Conclusions:
- The mdr2 gene is a distinct member of the mammalian mdr gene family, originating from a common ancestor with mdr1.
- The structural characteristics of the mdr2 protein suggest it functions in membrane transport.
- Further studies using gene-specific probes and antibodies are needed to elucidate mdr2's role in multidrug resistance and normal physiology.