Dynamics of co-translational protein targeting

Most membrane and secretory proteins are delivered co-translationally to protein translocation channels in their destination membrane by the signal recognition particle (SRP) and its receptor. This co-translational molecular machinery is conserved across all kingdoms of life, though it varies in composition and function. Here we report recent progress towards understanding the mechanism of SRP function, focusing on findings about Escherichia coli SRP's conformational dynamics throughout the targeting process. These insights shed light on a key checkpoint in the targeting cycle: how SRP regulates engagement of an actively translating ribosome with the translocation machinery at the membrane

Development of a heme protein structure-electrochemical function database. Nucleic Acids Res

ABSTRACT Proteins containing heme, iron(protoporphyrin IX) and its variants, continue to be one of the moststudied classes of biomolecules due to their diverse range of biological functions. The literature is abundant with reports of structural and functional characterization of individual heme proteins which demonstrate that heme protein reduction potential values, E m , span the range from -550 mV to +450 mV versus SHE. In order to unite these data for the purposes of global analysis, a new webbased resource of heme protein structure-function relationships is presented: the Heme Protein Database (HPD). This database is the first of its kind to combine heme protein structural classifications including protein fold, heme type and heme axial ligands, with heme protein reduction potential values in a web-searchable format. The HPD is located at http://heme.chem.columbia.edu/heme. php. The data illustrate that heme protein E m values are modulated over a 300 mV range by the type of global protein fold, a 600 mV range by the type of porphyrin and an 800 mV range by the axial ligands. Thus, the 1 V range observed in heme protein reduction potential values in biological systems arises from subtle combinations of these various factors

Signal Recognition Particle-ribosome Binding Is Sensitive to Nascent Chain Length*

The signal recognition particle (SRP) directs ribosome-nascent chain complexes (RNCs) displaying signal sequences to protein translocation channels in the plasma membrane of prokaryotes and endoplasmic reticulum of eukaryotes. It was initially proposed that SRP binds the signal sequence when it emerges from an RNC and that successful binding becomes impaired as translation extends the nascent chain, moving the signal sequence away from SRP on the ribosomal surface. Later studies drew this simple model into question, proposing that SRP binding is unaffected by nascent chain length. Here, we reinvestigate this issue using two novel and independent fluorescence resonance energy transfer assays. We show that the arrival and dissociation rates of SRP binding to RNCs vary according to nascent chain length, resulting in the highest affinity shortly after a functional signal sequence emerges from the ribosome. Moreover, we show that SRP binds RNCs in multiple and interconverting conformations, and that conversely, RNCs exist in two conformations distinguished by SRP interaction kinetics

Healthcare Resource Utilization and Costs Among Patients With Gastroesophageal Reflux Disease, Barrett’s Esophagus, and Barrett’s Esophagus-Related Neoplasia in the United States

**Background:** Gastroesophageal reflux disease (GERD) is a risk factor for Barrett’s esophagus (BE) and BE-related neoplasia (BERN). **Objectives:** This study aimed to evaluate healthcare resource utilization (HRU) and costs associated with GERD, BE, and BERN in the United States. **Methods:** Adult patients with GERD, nondysplastic BE (NDBE), and BERN (including indefinite for dysplasia $$IND$$, low-grade dysplasia $$LGD$$, high-grade dysplasia $$HGD$$ or esophageal adenocarcinoma $$EAC$$), were identified from a large US administrative claims database, the IBM Truven Health MarketScan® databases (Q1/2015-Q4/2019). Patients were categorized into the corresponding mutually exclusive EAC-risk/diagnosis cohorts based on the most advanced stage from GERD to EAC using diagnosis codes in medical claims. Disease-related HRU and costs (2020 USD) were calculated for each cohort. **Results:** Patients were categorized into the following EAC-risk/diagnosis cohorts: 3 310 385 into GERD, 172 481 into NDBE, 11 516 into IND, 4332 into LGD, 1549 into HGD, and 11 676 into EAC. Disease-related annual mean number of inpatient admissions, office visits, and emergency department visits by cohort were 0.09, 1.45, and 0.19 for GERD; 0.08, 1.55, and 0.10 for NDBE; 0.10, 1.92, and 0.13 for IND; 0.09, 2.05, and 0.10 for LGD; 0.12, 2.16, and 0.14 for HGD; and 1.43, 6.27, and 0.87 for EAC. Disease-related annual mean total healthcare costs by cohort were $6955 for GERD,$8755 for NDBE, $9675 for IND,$12 241 for LGD, 24 239 for HGD, and 146 319 for EAC. **Discussion:** Patients with GERD, BE, and BERN had important HRU and costs, including inpatient admissions and office visits. As patients progressed to more advanced stages, there was substantially higher disease-related resource utilization, with associated costs being 16 times higher in patients with EAC than those with NDBE. **Conclusions:** Findings suggest the need for early identification of high-risk individuals prior to progression to EAC to potentially improve clinical and economic outcomes in this population