Search results for "Transmembrane"
showing 10 items of 299 documents
Differences in the Association of BH3-Only Proteins to Biological Membranes
2017
Apoptosis, a prevalent mechanism of programmed cell death, is regulated by the Bcl-2 protein family. The balance between pro- and anti-apoptotic Bcl-2 members in the mitochondrial outer membrane (MOM) protects or triggers MOM permeabilization. Bcl-2 homology-3 (BH3)-only proteins participate in this process activating pro-apoptotic effectors and promoting permeabilization of the MOM. The membrane association of BH3-only proteins is controversial due to the lack of a canonical carboxyl-terminal (C-terminal) transmembrane (TM) domain. We used an in vitro transcription/translation system to study the insertion capacity of these hydrophobic C-terminal regions of the BH3-members Bik, Bim, Noxa, …
Shedding of interleukin-6 receptor and tumor necrosis factor alpha. Contribution of the stalk sequence to the cleavage pattern of transmembrane prote…
2000
A functionally and structurally diverse group of transmembrane proteins including transmembrane forms of mediators or receptors can be proteolytically cleaved to form soluble growth factors or receptors. Recently, the proteolytic activity responsible for pro-tumor necrosis factor alpha (proTNFalpha) processing has been identified and named TACE (TNFalpha converting enzyme). In experiments with TACE deficient (TACE-/-) fibroblasts we found that 4beta-phorbol 12-myristate 13-acetate (PMA)-induced shedding of the interleukin-6 receptor (IL-6R) is strongly reduced. A basal hydroxamate sensitive release of IL-6R, however, could still be detected. This result demonstrates that TACE plays a role i…
Functional and structural insights into astacin metallopeptidases
2012
The astacins are a family of multi-domain metallopeptidases with manifold functions in metabolism. They are either secreted or membrane-anchored and are regulated by being synthesized as inactive zymogens and also by colocalizing protein inhibitors. The distinct family members consist of N-terminal signal peptides and pro-segments, zincdependent catalytic domains, further downstream extracellular domains, transmembrane anchors, and cytosolic domains. The catalytic domains of four astacins and the zymogen of one of these have been structurally characterized and shown to comprise compact ~200-residue zinc-dependent moieties divided into an N-terminal and a C-terminal sub-domain by an active-s…
Sensing by the membrane-bound sensor kinase DcuS: exogenous versus endogenous sensing of C(4)-dicarboxylates in bacteria.
2010
Bacteria are able to grow at the expense of both common (succinate, L-malate, fumarate and aspartate) and uncommon (L-tartrate and D-malate) C4-dicarboxylates, which are components of central metabolism. Two types of sensors/regulators responding to the C4-dicarboxylates function in Escherichia coli, Bacillus, Lactobacillus and related bacteria. The first type represents membrane-integral two-component systems, while the second includes cytoplasmic LysR-type transcriptional regulators. The difference in location and substrate specificity allows the exogenous induction of metabolic genes by common C4-dicarboxylates, and endogenous induction by uncommon C4-dicarboxylates. The two-component s…
Conversion of the Sensor Kinase DcuS to the Fumarate Sensitive State by Interaction of the Bifunctional Transporter DctA at the TM2/PAS
2021
The membrane-bound C4-dicarboxylate (C4DC) sensor kinase DcuS of Escherichia coli typically forms a protein complex with the C4DC transporter DctA. The DctA × DcuS complex is able to respond to C4DCs, whereas DcuS without DctA is in the permanent ON state. In DctA, the C-terminal helix 8b (H8b) serves as the site for interaction with DcuS. Here the interaction site in DcuS and the related structural and functional adaptation in DcuS were determined. The Linker connecting transmembrane helix 2 (TM2) and the cytosolic PASC (Per-ARNT-SIM) domain of DcuS, was identified as the major site for interaction with DctA-H8b by in vivo interaction studies. The Linker is known to convert the piston-type…
Treatment of Pulmonary Disease of Cystic Fibrosis: A Comprehensive Review.
2021
Cystic fibrosis (CF) is a genetic disease that causes absence or dysfunction of a protein named transmembrane conductance regulatory protein (CFTR) that works as an anion channel. As a result, the secretions of the organs where CFTR is expressed are very viscous, so their functionality is altered. The main cause of morbidity is due to the involvement of the respiratory system as a result of recurrent respiratory infections by different pathogens. In recent decades, survival has been increasing, rising by around age 50. This is due to the monitoring of patients in multidisciplinary units, early diagnosis with neonatal screening, and advances in treatments. In this chapter, we will approach t…
Structure of the Human TRPML2 Ion Channel Extracytosolic/Lumenal Domain.
2019
Summary TRPML2 is the least structurally characterized mammalian transient receptor potential mucolipin ion channel. The TRPML family hallmark is a large extracytosolic/lumenal domain (ELD) between transmembrane helices S1 and S2. We present crystal structures of the tetrameric human TRPML2 ELD at pH 6.5 (2.0 A) and 4.5 (2.95 A), corresponding to the pH values in recycling endosomes and lysosomes. Isothermal titration calorimetry shows Ca2+ binding to the highly acidic central pre-pore loop which is abrogated at low pH, in line with a pH-dependent channel regulation model. Small angle X-ray scattering confirms the ELD dimensions in solution. Changes in pH or Ca2+ concentration do not affect…
The Surfactant Peptide KL4 Sequence Is Inserted with a Transmembrane Orientation into the Endoplasmic Reticulum Membrane
2008
AbstractSurfactant protein B (SP-B) is an essential component of pulmonary surfactant. Synthetic surfactant peptide KL4, a peptide based on a C-terminal amphipathic helical region of human SP-B, efficiently mimics some functional properties of SP-B and is included in therapeutic surfactant preparations used in trials to treat respiratory distress syndrome. The membrane orientation of this peptide is controversial. We used an in vitro transcription-translation system to study the insertion of hydrophobic sequences into microsomal membranes, and showed that the KL4 sequence integrates efficiently with a transmembrane orientation despite the presence of intermittent lysines throughout the sequ…
Distant downstream sequence determinants can control N-tail translocation during protein insertion into the endoplasmic reticulum membrane.
2000
We have studied the membrane insertion of ProW, an Escherichia coli inner membrane protein with seven transmembrane segments and a large periplasmic N-terminal tail, into endoplasmic reticulum (ER)-derived dog pancreas microsomes. Strikingly, significant levels of N-tail translocation is seen only when a minimum of four of the transmembrane segments are present; for constructs with fewer transmembrane segments, the N-tail remains mostly nontranslocated and the majority of the molecules adopt an 'inverted' topology where normally nontranslocated parts are translocated and vice versa. N-tail translocation can also be promoted by shortening of the N-tail and by the addition of positively charg…
Charge Pair Interactions in Transmembrane Helices and Turn Propensity of the Connecting Sequence Promote Helical Hairpin Insertion
2013
alpha-Helical hairpins, consisting of a pair of closely spaced transmembrane (TM) helices that are connected by a short interfacial turn, are the simplest structural motifs found in multi-spanning membrane proteins. In naturally occurring hairpins, the presence of polar residues is common and predicted to complicate membrane insertion. We postulate that the pre-packing process offsets any energetic cost of allocating polar and charged residues within the hydrophobic environment of biological membranes. Consistent with this idea, we provide here experimental evidence demonstrating that helical hairpin insertion into biological membranes can be driven by electrostatic interactions between clo…