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Transmembrane segments of the P-type cation-transporting ATPases. A comparative study
R K Nakamoto1, R Rao, C W Slayman
1Department of Human Genetics, Yale School of Medicine, New Haven, Connecticut 06510.
Annals of the New York Academy of Sciences
|January 1, 1989
Summary
This study models the Neurospora H-ATPase, revealing distinct patterns of charged and bulky residues at the membrane surface and within the bilayer. These findings suggest a role in cation transport and structural organization for the H-ATPase protein.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- The Neurospora H-ATPase is a P-type ATPase involved in proton transport.
- Understanding the membrane topology and residue distribution is crucial for elucidating its function.
- Previous models have provided insights into the structure of various ATPases.
Purpose of the Study:
- To model the transmembrane segments of the Neurospora H-ATPase.
- To analyze the distribution of charged and bulky residues within the membrane.
- To infer functional implications of the predicted structure, particularly in relation to cation transport.
Main Methods:
- Analysis of predicted transmembrane segments of the Neurospora H-ATPase.
- Diagrammatic representation of eight transmembrane segments.
- Comparison of charge distribution with other transport proteins.
Main Results:
- Transmembrane segments vary in length, ranging from 20 to 30 residues.
- A net excess of negative charges is observed at the extracellular surface (5-, 1+), and a slight excess of positive charges at the cytoplasmic surface (4+, 3-).
- Bulky residues (Trp, Phe, Tyr) are concentrated just inside the membrane, and helices are amphipathic, suggesting a channel-like structure.
Conclusions:
- The predicted model of Neurospora H-ATPase reveals specific charge and residue patterns consistent with cation transport.
- The amphipathic nature of helices supports the formation of a hydrophilic core and hydrophobic surface.
- The observed charge distribution differs from other unrelated transport proteins, highlighting P-type ATPase specificity.