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Complete amino acid sequence of the Aspergillus cytotoxin mitogillin
Abstract:
The complete amino acid sequence of the cytotoxin mitogillin has been determined by sequencing the intact chain and peptide fragments produced by cleavage at methionyl, arginyl, lysyl, and tryptophanyl residues and at one aspartic acid-proline bond. The protein consists of 149 amino acid residues with alanine at the NH2 terminus and histidine at the COOH terminus. The calculated Mr of the native mitogillin was 16 867. The native molecule presents two disulfide bridges, one between cysteine residues at positions 5 and 147 and another one between cysteine residues at positions 75 and 131. The amino acid sequence of mitogillin shows 86% homology with another cytotoxic protein called alpha-sarcin.
Insights
The complete amino acid sequence of the cytotoxin mitogillin was determined, revealing 149 residues and structural similarities to alpha-sarcin. This cytotoxic protein has alanine at its N-terminus and histidine at its C-terminus.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Mitogillin is a cytotoxic protein with known biological activity.
- Understanding the primary structure of cytotoxins is crucial for elucidating their function and mechanism of action.
Purpose of the Study:
- To determine the complete amino acid sequence of the cytotoxin mitogillin.
- To identify key structural features, including termini and disulfide bridges.
- To compare the sequence homology with other known cytotoxic proteins.
Main Methods:
- Sequencing of the intact mitogillin chain.
- Peptide fragmentation using specific cleavage sites (methionyl, arginyl, lysyl, tryptophanyl, and aspartic acid-proline bonds).
- Analysis of peptide fragments to deduce the full amino acid sequence.
Main Results:
- The complete amino acid sequence of mitogillin was established, comprising 149 residues.
- Alanine was identified as the N-terminal residue and histidine as the C-terminal residue.
- Two disulfide bridges were located between cysteine residues at positions 5-147 and 75-131.
- Mitogillin exhibits 86% amino acid sequence homology with alpha-sarcin.
Conclusions:
- The primary structure of mitogillin has been fully elucidated.
- The determined sequence and disulfide bridge information provide insights into mitogillin's three-dimensional structure and function.
- The high homology with alpha-sarcin suggests potential functional similarities between these cytotoxic proteins.