+検索条件
-Structure paper
タイトル | A Na pump with reduced stoichiometry is up-regulated by brine shrimp in extreme salinities. |
---|---|
ジャーナル・号・ページ | Proc Natl Acad Sci U S A, Vol. 120, Issue 52, Page e2313999120, Year 2023 |
掲載日 | 2023年12月26日 |
著者 | Pablo Artigas / Dylan J Meyer / Victoria C Young / Kerri Spontarelli / Jessica Eastman / Evan Strandquist / Huan Rui / Benoît Roux / Matthew A Birk / Hanayo Nakanishi / Kazuhiro Abe / Craig Gatto / |
PubMed 要旨 | Brine shrimp () are the only animals to thrive at sodium concentrations above 4 M. Salt excretion is powered by the Na,K-ATPase (NKA), a heterodimeric (αβ) pump that usually exports 3Na in exchange ...Brine shrimp () are the only animals to thrive at sodium concentrations above 4 M. Salt excretion is powered by the Na,K-ATPase (NKA), a heterodimeric (αβ) pump that usually exports 3Na in exchange for 2 K per hydrolyzed ATP. express several NKA catalytic α-subunit subtypes. High-salinity adaptation increases abundance of α2, an isoform that contains two lysines (Lys308 and Lys758 in transmembrane segments TM4 and TM5, respectively) at positions where canonical NKAs have asparagines ( α1's Asn333 and Asn785). Using de novo transcriptome assembly and qPCR, we found that express two salinity-independent canonical α subunits (α1 and α3), as well as two β variants, in addition to the salinity-controlled α2. These β subunits permitted heterologous expression of the α2 pump and determination of its CryoEM structure in a closed, ion-free conformation, showing Lys758 residing within the ion-binding cavity. We used electrophysiology to characterize the function of α2 pumps and compared it to that of α1 (and its α2-mimicking single- and double-lysine substitutions). The double substitution N333K/N785K confers α2-like characteristics to α1, and mutant cycle analysis reveals energetic coupling between these two residues, illustrating how α2's Lys308 helps to maintain high affinity for external K when Lys758 occupies an ion-binding site. By measuring uptake under voltage clamp of the K-congener Rb, we prove that double-lysine-substituted pumps transport 2Na and 1 K per catalytic cycle. Our results show how the two lysines contribute to generate a pump with reduced stoichiometry allowing to maintain steeper Na gradients in hypersaline environments. |
リンク | Proc Natl Acad Sci U S A / PubMed:38079564 / PubMed Central |
手法 | EM (単粒子) |
解像度 | 3.44 Å |
構造データ | EMDB-36794, PDB-8k1l: |
化合物 | ChemComp-ALF: |
由来 |
|
キーワード | TRANSPORT PROTEIN / P-type ATPase / sodium pump / membrane protein / transporter |