NhaA Antiporter Functions Using 10 Helices, and an Additional 2 Contribute to Assembly/stability

Overview

Journal Proc Natl Acad Sci U S A

Specialty Science

Date 2015 Sep 30

PMID 26417087

Citations 10

Authors

Etana Padan

Tsafi Danieli

Yael Keren

Dudu Alkoby

Gal Masrati

Turkan Haliloglu

Nir Ben-Tal

Abraham Rimon

Affiliations

Soon will be listed here.

Abstract

The Escherichia coli Na(+)/H(+) antiporter (Ec-NhaA) is the best-characterized of all pH-regulated Na(+)/H(+) exchangers that control cellular Na(+) and H(+) homeostasis. Ec-NhaA has 12 helices, 2 of which (VI and VII) are absent from other antiporters that share the Ec-NhaA structural fold. This α-hairpin is located in the dimer interface of the Ec-NhaA homodimer together with a β-sheet. Here we examine computationally and experimentally the role of the α-hairpin in the stability, dimerization, transport, and pH regulation of Ec-NhaA. Evolutionary analysis (ConSurf) indicates that the VI-VII helical hairpin is much less conserved than the remaining transmembrane region. Moreover, normal mode analysis also shows that intact NhaA and a variant, deleted of the α-hairpin, share similar dynamics, suggesting that the structure may be dispensable. Thus, two truncated Ec-NhaA mutants were constructed, one deleted of the α-hairpin and another also lacking the β-sheet. The mutants were studied at physiological pH in the membrane and in detergent micelles. The findings demonstrate that the truncated mutants retain significant activity and regulatory properties but are defective in the assembly/stability of the Ec-NhaA dimer.

Citing Articles

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