Number Distribution of Transmembrane Helices in Prokaryote Genomes

AbstractMicrobial rhodopsins are distributed through many microorganisms. Heliorhodopsins are newly discovered but have an unclear function. They have seven transmembrane helices similar to type-I and type-II rhodopsins, but they are different in that the N-terminal region of heliorhodopsin is cytoplasmic. We chose 13 representative heliorhodopsins from various microorganisms, expressed and purified with an N-terminal His tag, and measured the absorption spectra. The 13 natural variants had an absorption maximum (λmax) in the range 530–556 nm similar to proteorhodopsin (λmax = 490–525 nm). We selected several candidate residues that influence rhodopsin color-tuning based on sequence alignment and constructed mutants via site-directed mutagenesis to confirm the spectral changes. We found two important residues located near retinal chromophore that influence λmax. We also predict the 3D structure via homology-modeling of Thermoplasmatales heliorhodopsin. The results indicate that the color-tuning mechanism of type-I rhodopsin can be applied to understand the color-tuning of heliorhodopsin.

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Interhelical H-Bonds Modulate the Activity of a Polytopic Transmembrane Kinase

Biomolecules ◽

10.3390/biom11070938 ◽

2021 ◽

Vol 11 (7) ◽

pp. 938

Author(s):

Juan Cruz Almada ◽

Ana Bortolotti ◽

Jean Marie Ruysschaert ◽

Diego de Mendoza ◽

María Eugenia Inda ◽

...

Keyword(s):

Histidine Kinase ◽

Adaptive Response ◽

Catalytic Domain ◽

Membrane Lipids ◽

Signal Transmission ◽

Expression System ◽

Lipid Homeostasis ◽

Transmembrane Helices ◽

Transmembrane Region

DesK is a Histidine Kinase that allows Bacillus subtilis to maintain lipid homeostasis in response to changes in the environment. It is located in the membrane, and has five transmembrane helices and a cytoplasmic catalytic domain. The transmembrane region triggers the phosphorylation of the catalytic domain as soon as the membrane lipids rigidify. In this research, we study how transmembrane inter-helical interactions contribute to signal transmission; we designed a co-expression system that allows studying in vivo interactions between transmembrane helices. By Alanine-replacements, we identified a group of polar uncharged residues, whose side chains contain hydrogen-bond donors or acceptors, which are required for the interaction with other DesK transmembrane helices; a particular array of H-bond- residues plays a key role in signaling, transmitting information detected at the membrane level into the cell to finally trigger an adaptive response.

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Familial hemiplegic migraine type 2 due to a novel missense mutation in ATP1A2

The Journal of Headache and Pain ◽

10.1186/s10194-021-01221-x ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Fabio Antonaci ◽

Sabrina Ravaglia ◽

Gaetano S. Grieco ◽

Stella Gagliardi ◽

Cristina Cereda ◽

...

Keyword(s):

Case Reports ◽

3D Structure ◽

Familial Hemiplegic Migraine ◽

Transmembrane Helices ◽

Hemiplegic Migraine ◽

Case Presentation ◽

Italian Family ◽

Protein Prediction ◽

Functional Consequences

Abstract Background The mechanisms of genotype-phenotype interaction in Familiar Hemiplegic migraine type 2 (FHM2) are still far from clear. Different ATP1A2 mutations have been described, with a spectrum of phenotypes ranging from mild to severe. No genotype-phenotype correlations have been attempted. Case presentation We describe an Italian family with FHM and a missense ATP1A2 variant (L425H) not previously described. The clinical picture was mild in all the affected members. Conclusions Co-segregation of the variant with the aura phenotype was complete in this family, suggesting a 100% penetrance. In silico protein prediction softwares indicate that this variant may change the 3D structure of ATPA1A2 at the cytoplasmic loop between the two central transmembrane helices. Milder FHM phenotypes are rarely reported in literature, likely because case reports are biased towards the most severe phenotypes, with milder forms possibly misdiagnosed as sporadic migraine with aura forms (MAs), even with complex auras. Further studies taking into account intra-familiar variability and functional consequences on the channel protein may help clarify genotype-phenotype correlations.

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Function Trumps Form in Two Sugar Symporters, LacY and vSGLT

International Journal of Molecular Sciences ◽

10.3390/ijms22073572 ◽

2021 ◽

Vol 22 (7) ◽

pp. 3572

Author(s):

Jeff Abramson ◽

Ernest M. Wright

Keyword(s):

Binding Site ◽

Sugar Transport ◽

Electrochemical Potential ◽

Inverted Repeats ◽

Side Chains ◽

Transmembrane Helices ◽

Central Cavity ◽

Potential Gradients ◽

Sodium Binding ◽

Major Facilitator

Active transport of sugars into bacteria occurs through symporters driven by ion gradients. LacY is the most well-studied proton sugar symporter, whereas vSGLT is the most characterized sodium sugar symporter. These are members of the major facilitator (MFS) and the amino acid-Polyamine organocation (APS) transporter superfamilies. While there is no structural homology between these transporters, they operate by a similar mechanism. They are nano-machines driven by their respective ion electrochemical potential gradients across the membrane. LacY has 12 transmembrane helices (TMs) organized in two 6-TM bundles, each containing two 3-helix TM repeats. vSGLT has a core structure of 10 TM helices organized in two inverted repeats (TM 1–5 and TM 6–10). In each case, a single sugar is bound in a central cavity and sugar selectivity is determined by hydrogen- and hydrophobic- bonding with side chains in the binding site. In vSGLT, the sodium-binding site is formed through coordination with carbonyl- and hydroxyl-oxygens from neighboring side chains, whereas in LacY the proton (H3O+) site is thought to be a single glutamate residue (Glu325). The remaining challenge for both transporters is to determine how ion electrochemical potential gradients drive uphill sugar transport.

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