Dissected antiporter modules establish minimal proton-conduction elements of the respiratory complex I.

The respiratory Complex I is a highly intricate redox-driven proton pump that powers oxidative phosphorylation across all domains of life. Yet, despite major efforts in recent decades, its long-range energy transduction principles remain highly debated. We create here minimal proton-conducting membrane modules by engineering and dissecting the key elements of the bacterial Complex I.

Cotranslational folding of alkaline phosphatase in the periplasm of Escherichia coli.

Cotranslational protein folding studies using Force Profile Analysis, a method where the SecM translational arrest peptide is used to detect folding-induced forces acting on the nascent polypeptide, have so far been limited mainly to small domains of cytosolic proteins that fold in close proximity to the translating ribosome. In this study, we investigate the cotranslational folding of the periplasmic, disulfide bond-containing Escherichia coli protein alkaline phosphatase (PhoA) in a wild-type strain background and a strain background devoid of the periplasmic thiol: disulfide interchange protein DsbA. We find that folding-induced forces can be transmitted via the nascent chain from the periplasm to the polypeptide transferase center in the ribosome, a distance of ~160 Å, and that PhoA appears to fold cotranslationally via at least two disulfide-stabilized folding intermediates.

Cotranslational folding cooperativity of contiguous domains of α-spectrin.

Proteins synthesized in the cell can begin to fold during translation before the entire polypeptide has been produced, which may be particularly relevant to the folding of multidomain proteins. Here, we study the cotranslational folding of adjacent domains from the cytoskeletal protein α-spectrin using force profile analysis (FPA). Specifically, we investigate how the cotranslational folding behavior of the R15 and R16 domains are affected by their neighboring R14 and R16, and R15 and R17 domains, respectively.

Mapping 123 million neonatal, infant and child deaths between 2000 and 2017.

Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2-to end preventable child deaths by 2030-we need consistently estimated data at the subnational level regarding child mortality rates and trends.

Force-Profile Analysis of the Cotranslational Folding of HemK and Filamin Domains: Comparison of Biochemical and Biophysical Folding Assays.

We have characterized the cotranslational folding of two small protein domains of different folds-the α-helical N-terminal domain of HemK and the β-rich FLN5 filamin domain-by measuring the force that the folding protein exerts on the nascent chain when located in different parts of the ribosome exit tunnel (force-profile analysis, or FPA), allowing us to compare FPA to three other techniques currently used to study cotranslational folding: real-time FRET, photoinduced electron transfer, and NMR. We find that FPA identifies the same cotranslational folding transitions as do the other methods, and that these techniques therefore reflect the same basic process of cotranslational folding in similar ways.

Small membrane proteins - elucidating the function of the needle in the haystack.

Membrane proteins are important mediators between the cell and its environment or between different compartments within a cell. However, much less is known about the structure and function of membrane proteins compared to water-soluble proteins. Moreover, until recently a subset of membrane proteins, those shorter than 100 amino acids, have almost completely evaded detection as a result of technical difficulties.

Decreased capacity for sodium export out of Arabidopsis chloroplasts impairs salt tolerance, photosynthesis and plant performance.

Salt stress is a widespread phenomenon, limiting plant performance in large areas around the world. Although various types of plant sodium/proton antiporters have been characterized, the physiological function of NHD1 from Arabidopsis thaliana has not been elucidated in detail so far. Here we report that the NHD1-GFP fusion protein localizes to the chloroplast envelope.

Membrane transport piece by piece: production of transmembrane peptides for structural and functional studies.

Membrane proteins are involved in all cellular processes from signaling cascades to nutrient uptake and waste disposal. Because of these essential functions, many membrane proteins are recognized as important, yet elusive, clinical targets. Recent advances in structural biology have answered many questions about how membrane proteins function, yet one of the major bottlenecks remains the ability to obtain sufficient quantities of pure and homogeneous protein.

Structural and functional analysis of transmembrane segment IV of the salt tolerance protein Sod2.

Sod2 is the plasma membrane Na(+)/H(+) exchanger of the fission yeast Schizosaccharomyces pombe. It provides salt tolerance by removing excess intracellular sodium (or lithium) in exchange for protons. We examined the role of amino acid residues of transmembrane segment IV (TM IV) ((126)FPQINFLGSLLIAGCITSTDPVLSALI(152)) in activity by using alanine scanning mutagenesis and examining salt tolerance in sod2-deficient S.

Structure and function of the human Na+/H+ exchanger isoform 1.

Sodium proton exchangers (NHEs) constitute a large family of polytopic membrane protein transporters found in organisms across all domains of life. They are responsible for the exchange of protons for sodium ions. In archaea, bacteria, yeast and plants they provide increased salt tolerance by removing sodium in exchanger for extracellular protons.

Dimeric structure of human Na+/H+ exchanger isoform 1 overproduced in Saccharomyces cerevisiae.

The Na(+)/H(+) exchanger isoform 1 (NHE1) is an integral membrane protein that regulates intracellular pH by extruding an intracellular H(+) in exchange for one extracellular Na(+). The human NHE1 isoform is involved in heart disease and cell growth and proliferation. Although details of NHE1 regulation and transport are being revealed, there is little information available on the structure of the intact protein.