Association between FABP2 Ala54Thr polymorphisms and type 2 diabetes mellitus risk: a HuGE Review and Meta‐Analysis

Many studies have examined the association between the FABP2 (rs1799883) Ala54Thr gene polymorphism and type 2 diabetes mellitus risk (T2DM) in various populations, but their results have been inconsistent. To assess this relationship more precisely, A HuGE review and meta‐analysis were performed. The PubMed and CNKI database was searched for case‐control studies published up to April 2014. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated. Ultimately, 13 studies, comprising 2020 T2DM cases and 2910 controls were included. Overall, for the Thr carriers (Ala/Thr and Thr/Thr) versus the wild‐type homozygotes (Ala/Ala), the pooled OR was 1.18 (95% CI = 1.04–1.34, P = 0.062 for heterogeneity), for Thr/Thr versus Ala/Ala the pooled OR was 1.17 (95% CI = 1.05–1.41 P = 0.087 for heterogeneity). In the stratified analysis by ethnicity, the significantly risks were found among Asians but not Caucasians. This meta‐analysis suggests that the FABP2 (rs1799883) Ala54Thr polymorphisms are associated with increased susceptibility to T2DM risk among Asians but not Caucasians.     

A fast dynamic mode of the EF‐G‐bound ribosome

A key intermediate in translocation is an ‘unlocked state’ of the pre‐translocation ribosome in which the P‐site tRNA adopts the P/E hybrid state, the L1 stalk domain closes and ribosomal subunits adopt a ratcheted configuration. Here, through two‐ and three‐colour smFRET imaging from multiple structural perspectives, EF‐G is shown to accelerate structural and kinetic pathways in the ribosome, leading to this transition. The EF‐G‐bound ribosome remains highly dynamic in nature, wherein, the unlocked state is transiently and reversibly formed. The P/E hybrid state is energetically favoured, but exchange with the classical P/P configuration persists; the L1 stalk adopts a fast dynamic mode characterized by rapid cycles of closure and opening. These data support a model in which P/E hybrid state formation, L1 stalk closure and subunit ratcheting are loosely coupled, independent processes that must converge to achieve the unlocked state. The highly dynamic nature of these motions, and their sensitivity to conformational and compositional changes in the ribosome, suggests that regulating the formation of this intermediate may present an effective avenue for translational control.     

Biosensors based on peptide exposure show single molecule conformations in live cells

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Evolutionary assembly of cooperating cell types in an animal chemical defense system

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Effects of detergents on catalytic activity of human endometase/matrilysin 2, a putative cancer biomarker

Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (∼ 90 μM). Their IC₅₀ values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon’s plot; however, the inhibition mechanism of endometase was noncompetitive with a K_i value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity.     

The application of strand invasion phenomenon,directed by peptide nucleic acid (PNA) and single‐stranded DNA binding protein (SSB) for the recognition of specific sequences of human endogenous retroviral HERV‐W family

The HERV‐W family of human endogenous retroviruses represents a group of numerous sequences that show close similarity in genetic composition. It has been documented that some members of HERV‐W–derived expression products are supposed to play significant role in humans' pathology, such as multiple sclerosis or schizophrenia. Other members of the family are necessary to orchestrate physiological processes (eg, ERVWE1 coding syncytin‐1 that is engaged in syncytiotrophoblast formation). Therefore, an assay that would allow the recognition of particular form of HERV‐W members is highly desirable. A peptide nucleic acid (PNA)–mediated technique for the discrimination between multiple sclerosis‐associated retrovirus and ERVWE1 sequence has been developed. The assay uses a PNA probe that, being fully complementary to the ERVWE1 but not to multiple sclerosis‐associated retrovirus (MSRV) template, shows high selective potential. Single‐stranded DNA binding protein facilitates the PNA‐mediated, sequence‐specific formation of strand invasion complex and, consequently, local DNA unwinding. The target DNA may be then excluded from further analysis in any downstream process such as single‐stranded DNA‐specific exonuclease action. Finally, the reaction conditions have been optimized, and several PNA probes that are targeted toward distinct loci along whole HERV‐W env sequences have been evaluated. We believe that PNA/single‐stranded DNA binding protein–based application has the potential to selectively discriminate particular HERV‐W molecules as they are at least suspected to play pathogenic role in a broad range of medical conditions, from psycho‐neurologic disorders (multiple sclerosis and schizophrenia) and cancers (breast cancer) to that of an auto‐immunologic background (psoriasis and lupus erythematosus).     

Significant impact of divalent metal ions on the fidelity,sugar selectivity,and drug incorporation efficiency of human PrimPol

Human PrimPol is a recently discovered bifunctional enzyme that displays DNA template-directed primase and polymerase activities. PrimPol has been implicated in nuclear and mitochondrial DNA replication fork progression and restart as well as DNA lesion bypass. Published evidence suggests that PrimPol is a Mn²⁺-dependent enzyme as it shows significantly improved primase and polymerase activities when binding Mn²⁺, rather than Mg²⁺, as a divalent metal ion cofactor. Consistently, our fluorescence anisotropy assays determined that PrimPol binds to a primer/template DNA substrate with affinities of 29 and 979 nM in the presence of Mn²⁺ and Mg²⁺, respectively. Our pre-steady-state kinetic analysis revealed that PrimPol incorporates correct dNTPs with 100-fold higher efficiency with Mn²⁺ than with Mg²⁺. Notably, the substitution fidelity of PrimPol in the presence of Mn²⁺ was determined to be in the range of 3.4 × 10⁻² to 3.8 × 10⁻¹, indicating that PrimPol is an error-prone polymerase. Furthermore, we kinetically determined the sugar selectivity of PrimPol to be 57–1800 with Mn²⁺ and 150–4500 with Mg²⁺, and found that PrimPol was able to incorporate the triphosphates of two anticancer drugs (cytarabine and gemcitabine), but not two antiviral drugs (emtricitabine and lamivudine).