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Synthesis and structure-activity study of myxoma virus growth factor
Abstract:
Myxoma virus growth factor (MGF) is an 85-residue peptide derived from the gene product of a DNA tumor virus that infects rabbits. The carboxyl domain of MGF possesses about 40% sequence homology with the epidermal growth factor (EGF). This EGF-like domain covering residues 30-83 was synthesized and found to possess putative activities of EGF. It was, however, about 200-fold less active than EGF in the competitive binding of EGF receptor in A431 cells and the stimulation of [3H]-thymidine uptake in NRK 49F cells. MGF(30-83) is a basic and a hydrophobic peptide rich in beta-sheet structure. These features in MGF tend to promote aggregation, leading to precipitation even in strongly denaturing solutions. Thus, the refolding of MGF was achieved with difficulty and resulted in low yield. To increase the synthetic yield of MGF(30-83), a cluster of acidic amino acids was added to the NH2-terminus of MGF(30-83). This approach was found to be effective in minimizing the refolding difficulties and allowed accessibility to the synthesis of analogues in this class of compounds. The relationships of structure and function of MGF were studied by using analogues with point substitution by the corresponding D-amino acid or by Ala at position 44 or 52 and analogues with deletion of basic residues from the amino terminus. Modifications of both the receptor contact and the structural residues greatly reduced the potency of MGF(30-83), and the overall result correlated well with the known structure-activity of the EGF family.
Insights
Myxoma virus growth factor (MGF) exhibits EGF-like activity but is less potent. Adding acidic amino acids improved MGF synthesis and enabled structure-activity studies of this EGF family member.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Myxoma virus growth factor (MGF) is a peptide derived from a rabbit DNA tumor virus.
- MGF shares sequence homology with epidermal growth factor (EGF), suggesting similar biological functions.
Purpose of the Study:
- To synthesize and characterize the EGF-like domain of MGF (MGF(30-83)).
- To investigate methods for improving MGF synthesis and explore its structure-activity relationships.
- To compare MGF's activity with EGF.
Main Methods:
- Chemical synthesis of the MGF(30-83) peptide.
- Modification of MGF(30-83) by adding acidic amino acids to the N-terminus.
- Creation of analogues with point substitutions (D-amino acids, Ala) and deletions.
- Assays for EGF receptor binding and [3H]-thymidine uptake stimulation.
Main Results:
- MGF(30-83) demonstrated putative EGF activities but was ~200-fold less potent than EGF in receptor binding and cell proliferation assays.
- MGF(30-83) is a basic, hydrophobic peptide prone to aggregation, complicating refolding and synthesis.
- Adding acidic amino acids to the N-terminus facilitated refolding and enabled analogue synthesis.
- Modifications to receptor contact and structural residues significantly reduced MGF(30-83) potency.
Conclusions:
- MGF(30-83) possesses reduced EGF-like activity, likely due to its structural properties and amino acid sequence.
- The strategy of adding acidic residues is effective for improving the synthesis of MGF and related compounds.
- Structure-activity studies confirm that modifications to key residues impact MGF's biological potency, consistent with the EGF family.