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A distant evolutionary relationship between bacterial sphingomyelinase and mammalian DNase I
Y Matsuo1, A Yamada, K Tsukamoto
1Protein Engineering Research Institute, Osaka, Japan.
Protein Science : a Publication of the Protein Society
|December 1, 1996
Summary
Bacterial sphingomyelinase (SMase) shares structural and functional similarities with mammalian DNase I, suggesting a distant evolutionary link. Key active site residues are conserved, crucial for enzyme activity and substrate recognition.
Area of Science:
- Biochemistry
- Structural Biology
- Evolutionary Biology
Background:
- Bacterial sphingomyelinase (SMase) is an enzyme involved in lipid metabolism.
- Understanding its structure-function relationship is crucial for biochemical studies.
Purpose of the Study:
- To predict the three-dimensional structure of bacterial SMase.
- To investigate its evolutionary relationship with other enzymes.
- To identify key residues involved in its catalytic activity and substrate recognition.
Main Methods:
- Protein fold recognition and sequence alignment were used to predict SMase structure.
- Site-directed mutagenesis was employed to study the function of specific residues.
- Molecular modeling was used to create a model of the SMase-sphingomyelin complex.
Main Results:
- Bacterial SMase shares structural similarity with mammalian DNase I.
- Conserved residues, including histidine and aspartate, are critical for SMase catalytic activity.
- Mutagenesis of key residues (H134A, H252A) abolished enzyme activity.
- A conserved pentapeptide motif was identified, specific to SMase and DNase I.
- A structural model suggested the role of specific residues in substrate recognition.
Conclusions:
- Bacterial SMase and mammalian DNase I share a distant evolutionary origin.
- Conserved residues and structural similarities highlight functional convergence.
- The study provides insights into the catalytic mechanism and substrate specificity of SMase.