Identification of domain interfaces in the E. coli mannitol permease

The Escherichica coli mannitol permease or enzyme IImtl (Ellmtl) catalyses the uptake and concomitant phosphorylation of mannitol Ellmtl has a complex architecture with each subunit of the dimer consisting of three domains (A, B, and C). Protein and domain interactions are needed to transfer the phosphoryl group from the A to the B domain, but also to accomplish the actual phosphorylation of the carbohydrate by the B domain, while bound to the C domain. In addition, the energy for the translocation step catalyzed by the membrane-embedded C domain comes from a conformational coupling interaction between the C and a phosphorylated B domain. Identification of the B/C domain and dimer interface should, therefore, assist in the elucidation of the energy-coupling mechanism and the conformational interaction in Ellmtl. Unfortunately, high-resolution structures are not available for the B and C domain of Ellmtl. Thus a variety of other approaches must be employed to u! nravel the details of these interactions. Some of them will be presented in this thesis. zie: Summary.

Improved in-gel approaches to generate peptide maps of integral membrane proteins with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

This paper reports studies of in-gel digestion procedures to generate MALDI-MS peptide maps of integral membrane proteins. The methods were developed for the membrane domain of the mannitol permease of E. coli. In-gel digestion of this domain with trypsin, followed by extraction of the peptides from the gel, yields only 44% sequence coverage. Since lysines and arginines are seldomly found in the membrane-spanning regions, complete tryptic cleavage will generate large hydrophobic fragments, many of which are poorly soluble and most likely contribute to the low sequence coverage. Addition of the detergent octyl-β-glucopyranoside (OBG), at 0.1% concentration, to the extraction solvent increases the total number of peptides detected to at least 85% of the total protein sequence. OBG facilitates the recovery of hydrophobic peptides when they are SpeedVac dried during the extraction procedure. Many of the newly recovered peptides are partial cleavage products. This seems to be advantageous since it generates hydrophobic fragments with a hydrophilic solubilizing part. In-gel CNBr cleavage resulted in 5–10-fold more intense spectra, 83% sequence coverage, fully cleaved fragments and no effect of OBG. In contrast to tryptic cleavage sites, the CNBr cleavage sites are found in transmembrane segments; cleavage at these sites generates smaller hydrophobic fragments, which are more soluble and do not need OBG. With the results of both cleavages, a complete sequence coverage of the membrane domain of the mannitol permease of E. coli is obtained without the necessity of using HPLC separation. The protocols were applied to two other integral membrane proteins, which confirmed the general applicability of CNBr cleavage and the observed effects of OBG in peptide recovery after tryptic digestion.

Combined in-gel tryptic digestion and CNBr cleavage for the generation of peptide maps of an integral membrane protein with MALDI-TOF mass spectrometry

A limitation of the in-gel approaches for the generation of peptides of membrane proteins is the size and hydrophobicity of the fragments generated. For membrane proteins like the lactose transporter (LacS) of Streptococcus thermophilus, tryptic digestion or CNBr cleavage yields several hydrophobic fragments larger than 3.5 kDa. As a result, the sequence coverage of the membrane domain is low when the in-gel tryptic-digested or CNBr-cleaved fragments are analyzed by matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS). The combination of tryptic digestion and subsequent CNBr cleavage on the same gel pieces containing LacS approximately doubled the coverage of the hydrophobic membrane domain compared to the individual cleavage methods, while the coverage of the soluble domain remained complete. The fragments formed are predominantly below m/z 2500, which allows accurate mass measurement.

HIV-1 envelope trimer has similar binding characteristics for carbohydrate-binding agents as monomeric gp120

AbstractThe native HIV-1 Env complex consists of a gp120/gp41 trimer, but surface plasmon resonance (SPR)-directed binding studies for gp120-binding agents were almost exclusively performed on monomeric gp120. SPR-directed binding kinetics of monomeric gp120 and trimeric gp140 were investigated for a broad variety of envelope (Env)-binding agents. Similar kinetics for carbohydrate-binding agents (CBAs), the antibody 2G12 and sCD4 were observed, irrespective of the oligomeric state of gp120 that either contain the native mixture of complex and high-mannose N-glycans or that contain exclusively oligomannose N-glycans. The generally comparable kinetic properties of CBA, 2G12 and sCD4 binding to monomeric gp120 and trimeric gp140 indicate that monomeric gp120 is a good surrogate molecule for native HIV-1 Env trimer to investigate the binding affinities of Env-binding compounds.Structured summary of protein interactionsgp120 binds to GRFT by surface plasmon resonance (View Interaction: 1, 2)gp120 binds to UDA by surface plasmon resonance (View Interaction: 1, 2)gp120 binds to AH by surface plasmon resonance (View Interaction: 1, 2

HIV-1 envelope trimer has similar binding characteristics for carbohydrate-binding agents as monomeric gp120

The native HIV-1 Env complex consists of a gp120/gp41 trimer, but surface plasmon resonance (SPR)-directed binding studies for gp120-binding agents were almost exclusively performed on monomeric gp120. SPR-directed binding kinetics of monomeric gp120 and trimeric gp140 were investigated for a broad variety of envelope (Env)-binding agents. Similar kinetics for carbohydrate-binding agents (CBAs), the antibody 2G12 and sCD4 were observed, irrespective of the oligomeric state of gp120 that either contain the native mixture of complex and high-mannose N-glycans or that contain exclusively oligomannose N-glycans. The generally comparable kinetic properties of CBA, 2G12 and sCD4 binding to monomeric gp120 and trimeric gp140 indicate that monomeric gp120 is a good surrogate molecule for native HIV-1 Env trimer to investigate the binding affinities of Env-binding compounds. STRUCTURED SUMMARY OF PROTEIN INTERACTIONS: gp120binds to GRFT by surface plasmon resonance (View Interaction: 1, 2) gp120binds to UDA by surface plasmon resonance (View Interaction: 1, 2) gp120binds to AH by surface plasmon resonance (View Interaction: 1, 2).status: publishe

Short- and long-term adverse events in patients on temporary circulatory support before durable ventricular assist device: An IMACS registry analysis

BACKGROUND: Patients with cardiogenic shock (CS) needing temporary circulatory support (TCS) have poor survival rates after implantation of durable ventricular assist device (dVAD). We aimed to characterize post-dVAD adverse event burden and survival rates in patients requiring pre-operative TCS. METHOD: We analyzed 13,511 adults (Interagency Registry for Mechanically Assisted Circulatory Support [INTERMACS] Profiles 1-3) with continuous-flow dVADs in International Society for Heart and Lung Transplantation Registry for Mechanically Assisted Circulatory Support (2013-2017) according to the need for pre-operative TCS (n = 5,632) vs no TCS (n = 7,879). Of these, 726 (5.4%) had biventricular assist devices (BiVAD). Furthermore, we compared prevalent rates (events/100 patient-months) of bleeding, device-related infection, hemorrhagic and ischemic cerebrovascular accidents (hemorrhagic cerebral vascular accident [hCVA], and ischemic cerebral vascular accident [iCVA]) in early (<3 months) and late (≥3 months) post-operative periods. RESULTS: TCS included extracorporeal membrane oxygenation (ECMO) (n = 1,138), intra-aortic balloon pump (IABP) (n = 3,901), and other TCS (n = 593). Within 3 post-operative months, there were more major bleeding and cerebrovascular accidents (CVAs) in patients with pre-operative ECMO (events/100 patient-months rates: bleeding = 19, hCVA = 1.6, iCVA = 2.8) or IABP (bleeding = 17.3, hCVA = 1.5, iCVA = 1.5) vs no TCS (bleeding = 13.2, hCVA = 1.1, iCVA = 1.2, all p < 0.05). After 3 months, adverse events were lower and similar in all groups. Patients with ECMO had the worst short- and long-term survival rates. Patients with BiVAD had the worst survival rate regardless of need for pre-operative TCS. CVA and multiorgan failures were the common causes of death for patients with TCS and patients without TCS. CONCLUSIONS: Patients requiring TCS before dVAD had a sicker phenotype and higher rates of early post-operative adverse events than patients without TCS. ECMO was associated with very high early ischemic stroke, bleeding, and mortality. The extreme CS phenotype needing ECMO warrants a higher-level profile status, such as INTERMACS "0."status: publishe