Uterine infusion strategies for infertile patients with recurrent implantation failure: a systematic review and network meta-analysis.

BACKGROUND: Intra-uterine infusion treatments were reported to be beneficial to embryo implantation and pregnancy outcomes, and considered as potential therapies for infertile patients with recurrent implantation failure (RIF). Nevertheless, their efficiencies were controversial and there lack of consensus on which intrauterine treatment is the most effective. METHODS: All prospective trials (in Chinese or English) were searched in Databases PubMed, Cochrane, Web of Science, and CNKI from July 2013 to July 2023. We included studies that investigated various uterine infusions, including chorionic gonadotropin, granulocyte colony-stimulating factor, monocytes, platelet-rich plasma, etc. during IVF treatment and reported subsequent pregnancy outcomes. RESULTS: We finally included 56 researches, including 40 randomized controlled trials, 14 non-randomized controlled trials, and 3 prospective cohort studies. This study included a total of 11 uterine perfusion methods: Placebo, Human Chorionic Gonadotropin (HCG), Granulocyte Colony-Stimulating Factor (G-CSF), platelet-rich plasma (PRP), Peripheral Blood Mononuclear Cell (PBMC), Growth hormone (GH), dexamethasone (DEX), Embryo culture supernatant (ESC), PRP combined with G-CSF (PRP + G-CSF), RPR combined with subcutaneous injection of G-CSF (RPR + G-CSFsc), G-CSF combined with subcutaneous injection of AXaIU (G-CSF + AXaIUsc). Intrauterine infusion of HCG, PBMC, G-CSF, and PRP significantly improves pregnancy outcomes in patients with repeated implantation failure compared with blank controls or placebo, and PRP improved the clinical pregnancy and live birth most. GH and ESC infusion might improve the pregnancy outcomes, but uterine infusion of DEX was shown with high miscarriage. The combination therapy did not show a significant advantage over the mono-therapy. CONCLUSIONS: Intrauterine infusion of HCG, PBMC, G-CSF, and PRP are promising strategies for improving pregnancy outcomes for infertile patients with recurrent implantation failure. Among these treatments, PRP may be the best. More researches are required to explore the effect of drug combinations and less commonly used drugs as well. TRIAL REGISTRATION: Our study was registered in PROSPERO and the ID was CRD42023467188.

Core competence of midwives in township hospitals and its influencing factors-A cross-sectional study.

Objective: This study aimed to assess the core competence of midwives in township hospitals through a self-assessment questionnaire. The relationship between professional identity and core competence and the factors influencing midwives' core competence was also investigated. Method: Convenience sampling was conducted in 77 township hospitals in Ganzhou, Jiangxi Province, China, with 150 participants. The questionnaires were distributed online in November 2021. We conducted a descriptive data analysis, a correlation analysis of the two variables of professional identity and core competencies, and multivariate linear regression to analyse the influencing factors, including the sociodemographic information, the Midwife Core Competence Scale, and the Nurses' Professional Identity Scale scores. Results: The mean score for the core competence was 206.43 (±37.45) out of 270. The highest score was for pregnancy care (3.97 ± 0.70) and the lowest was for newborn care (3.72 ± 0.78). The independent sample t-test results and one-way analysis of variance showed that qualifications, midwifery training situation, and midwifery working years had differential effects on midwives' core competencies (P < 0.05). Multiple linear regression showed that qualifications, midwifery working years, and level of professional identity were influencing factors (P < 0.05). Conclusions: The core competencies of midwives in township hospitals were lower than those reported in other studies. Advancements in education, midwifery working years, and professional identity may increase midwives' core competencies.

Effect of radiation fractionation on IDO1 via the NF-κB/COX2 axis in non-small cell lung cancer.

Radiotherapy (RT) is the mainstay treatment modality for lung cancer. We recently reported that conventionally fractionated radiotherapy (CRT) with daily fractionation of 2Gy significantly increased the activity of indoleamine 2,3-dioxygenase (IDO1), a known immune checkpoint, which predicted poorer long-term survival in patients with non-small cell lung cancer (NSCLC), while stereotactic body radiotherapy (SBRT) using fractionation size of 10Gy did not increase IDO1 activity and had better survival. Here we hypothesized that the hypofractionated SBRT kind of dose fraction stimulates host antitumor immunity via downregulating IDO1 in which CRT could not. We tested this hypothesis in vitro and in vivo using 10Gyx1 and 2Gyx8 fractionations in the laboratory. The results demonstrated that, although there was an initial downregulation after RT, the expression of IDO1 was ultimately upregulated by both fractionation regimens. The 10Gyx1 regimen had minimum upregulation, while the 2Gyx8 regimen significantly increased in IDO1 expression which was positively correlated with the elevated expressions of p-NF-κB and COX2. Pharmacological inhibition of COX2 abolished RT-induced IDO1 expression. Furthermore, the IDO1 inhibitor, D-1-methyl-tryptophan (D-1MT), exerted RT-related tumor-killing effects in the NSCLC cell lines and mouse models. These findings suggest that, in addition to being an immune suppressor, IDO1 may serve as an adaptive resistance factor in RT. Furthermore, an unappreciated mechanism may exist, where a larger fraction size might be superior to conventional sizes in cancer treatment. This study may provide a rationale for future research in using IDO1 as a biomarker to personalize RT dose fractionation and COX2 inhibitor to decrease radiation immune suppression from CRT.

Thyroid autoimmunity and future pregnancy outcome in women of recurrent pregnancy loss: a meta-analysis.

BACKGROUND: Thyroid autoimmunity (TAI) has been associated with the risk of recurrent pregnancy loss (RPL). This systematic review and meta-analysis was conducted to evaluate the influence of TAI on subsequent pregnancy outcome of women with RPL. METHODS: A systematic search of Medline, Web of Science, and Embase was conducted to identify studies evaluating the influence of TAI on subsequent risk of pregnancy loss (PL) in women with RPL. Study quality was evaluated via the Newcastle-Ottawa Scale. A random-effects model was utilized to pool the results, accounting for heterogeneity. RESULTS: Ten observational studies were included. Compared to women without thyroid autoantibodies, RPL women with TAI had a higher risk of PL in their subsequent pregnancy (risk ratio [RR]: 1.46. 95% confidence interval [CI]: 1.20 to 1.78, p < 0.001; I2 = 35%). Sensitivity analyses showed consistent results in studies with thyroid peroxidase antibody positivity (RR: 1.50, 95% CI: 1.23 to 1.82) and in studies with TAI assessed before pregnancy (RR: 1.28, 95% CI: 1.07 to 1.53). Subgroup analyses showed that the results were not significantly different in prospective and retrospective studies, in RPL defined as at least two or three PL, in euthyroid women and women with euthyroidism or subclinical hypothyroidism, in women with and without levothyroxine treatment, in studies reporting first-trimester or overall PL, and in studies with different quality scores (p for subgroup difference all > 0.05). CONCLUSIONS: In women with RPL, positive for TAI may be related to a higher risk of PL in subsequent pregnancy.

Emerging roles of PHLPP phosphatases in lung cancer.

Pleckstrin homologous domain leucine-rich repeating protein phosphatases (PHLPPs) were originally identified as protein kinase B (Akt) kinase hydrophobic motif specific phosphatases to maintain the cellular homeostasis. With the continuous expansion of PHLPPs research, imbalanced-PHLPPs were mainly found as a tumor suppressor gene of a variety of solid tumors. In this review, we simply described the history and structures of PHLPPs and summarized the recent achievements in emerging roles of PHLPPs in lung cancer by 1) the signaling pathways affected by PHLPPs including Phosphoinositide 3-kinase (PI3K)/AKT, RAS/RAF/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) and Protein kinase C (PKC) signaling cascades. 2) function of PHLPPs regulatory factor USP46 and miR-190/miR-215, 3) the potential roles of PHLPPs in disease prognosis, Epidermal growth factor receptors (EGFR)- tyrosine kinase inhibitor (TKI) resistance and DNA damage, 4) and the possible function of PHLPPs in radiotherapy, ferroptosis and inflammation response. Therefore, PHLPPs can be considered as either biomarker or prognostic marker for lung cancer treatment.

Recurrent trichilemmal carcinoma of the periorbital region treated with IMRT radiotherapy: A case report and a review of literature.

RATIONALE: Trichilemmal carcinoma (TLC) is a rare malignant cutaneous adnexal tumor usually accept surgery. This report describes an elderly patient with recurrence TLC of the periorbital region after surgery who was subsequently treated with IMRT radiotherapy. After 2-years follow-up visit, there was no progress or metastasis. INTRODUCTION: TLC is a rare malignant cutaneous adnexal tumor. It usually occurs on sun-exposed areas in elderly people but rarely occurs in the periorbital region. Most cases accept surgery or micrographic Mohs surgery. Recurrence or metastasis of this neoplasm was seldom reported in the medical literature after enough tumor-free margin surgery. And radiotherapy was seldom reported in the treatment for patients of TLC. PATIENT CONCERNS: Here we report an elderly patient with recurrence TLC of the periorbital region after surgery who was subsequently treated with radiotherapy with a total dose of 66 Gy. Two years later, the patient was admitted head, neck, chest, abdomen CT scan, and no progress or metastasis was detected after 2-years follow-up. DIAGNOSIS: Trichilemmal carcinoma of the periorbital region. INTERVENTIONS: We describe the clinical characteristics, pathological features, and choice of examination methods of a patient with TLC in the periorbital region. And we use the radical radiotherapy to treat this case. OUTCOMES: There are no progress or metastasis after 2-years follow-up. CONCLUSION: Radiotherapy is a good option for patients with TLC if the patient refuses surgery or fails to achieve a satisfactory tumor-free margin or relapses after surgery.

Synergistic Antitumor Effects of Anlotinib Combined with Oral 5-Fluorouracil/S-1 via Inhibiting Src/AKT Signaling Pathway in Small-Cell Lung Cancer.

Background: Small-molecule tyrosine inhibitor anlotinib which developed in China has been approved as a third-line treatment for patients with small-cell lung cancer (SCLC). Our previous clinical study found that anlotinib combined with S-1 has better short-term ORR than the single-agent anlotinib of SCLC and other small-molecule vascular targeted drug therapies in the treatment of SCLC. However, the molecular mechanism of those effect remains unclear. Methods: SCLC cell line H446 was treated with either anlotinib, 5-FU alone, or combination. The cellular effects including cell viability, cell apoptosis, cell cycle, cell migration, and invasion were explored to evaluate the cell proliferation level. Western blot was performed to determine the protein levels of the combined action of the two drugs. The xenograft mouse model was established by injection of H446 cells into mouse, and the animals were randomized and assigned for the drug treatments. Body weights and tumor sizes were recorded. WB was conducted using tumor tissues. All data were collected and statistically analyzed using t-test to reveal the underlying molecular mechanism. Results: When anlotinib was combined with 5-FU, the IC50 value of cells was significantly reduced. And apoptosis, cell cycle arrest, and cell motility rates were stronger when anlotinib combined with 5-FU than in the anlotinib or 5-FU alone. In H446 cell-derived xenograft mouse model, tumor volumes were significantly decreased in Anlo/5-FU combination group than anlotinib or 5-FU alone group. Western blot showed the decreasing expression of p-Src/p-AKT in the Anlo/5-FU group. Conclusion: Our data revealed that the treatment of combination of antitumor angiogenesis agent anlotinib with chemotherapy drug 5-FU may have synergistic cytotoxicity to SCLC in vitro and in vivo. This treatment modality reduced cell proliferation and migration via Src/AKT pathway. This new strategy may be a promising treatment for SCLC but needs to be confirmed in future clinical trials.

Chemerin promotes the pathogenesis of preeclampsia by activating CMKLR1/p-Akt/CEBPɑ axis and inducing M1 macrophage polarization.

A higher ratio of M1/M2 macrophages and an elevated chemerin level are both related to increased risk of preeclampsia. However, the crosstalk between these two events and their collective contribution to preeclampsia are not well understood. In this study, we assessed the impacts of chemerin chemokine-like receptor 1 (CMKLR1)/p-Akt/CEBPα axis in regulating macrophage polarization and mediating the pathogenic effects of chemerin on preeclampsia. We showed that chemerin, in a dose- and time-dependent manner, stimulated M1 macrophage polarization, inhibited macrophage-induced trophoblast invasion and migration, and suppressed macrophage-mediated angiogenesis. All these chemerin-induced phenotypes are essentially mediated by sequentially CMKLR1, Akt activation, and CEBPα. Mechanistically, CEBPα acted as a transcriptional activator for both IRF8 and chemerin. In vivo, chemerin aggravated preeclampsia, while α-NETA, an inhibitor for CMKLR1, significantly suppressed M1 macrophage polarization and alleviated preeclampsia. In summary, chemerin, by activating CMKLR1/Akt/CEBPα axis, forms a positive feedback loop, promotes M1 macrophage polarization, suppresses trophoblast migration/invasion and angiogenesis, and contributes to preeclampsia. Therefore, targeting chemerin signaling may benefit the prevention and/or treatment of preeclampsia.

Gonadotropin versus Follicle-Stimulating Hormone for Ovarian Response in Patients Undergoing in vitro Fertilization: A Retrospective Cohort Comparison.

BACKGROUND: Poor ovarian responders generally refer to patients who respond poorly to ovarian stimulation for assisted reproductive techniques (ART) such as in-vitro fertilization (IVF) and hence experience low live birth rate. Various controlled ovarian stimulation (COS) protocols have been developed during the past 3 decades for IVF/ICSI to improve oocyte quality and ultimately live birth rate, to increase ovarian response in POR patients, and to reduce the risk of ovarian hyperstimulation syndrome. Both highly puri?ed human menopausal gonadotropin (hp-hMG) and recombinant follicle-stimulating hormone (rFSH) have been widely used for COS during IVF/ICSI. Their in?uence on treatment outcome in women undergoing IVF/ICSI hasbeen actively debated. OBJECTIVES: To compare highly purified human menopausal gonadotropin (hp-hMG) and recombinant follicle-stimulating hormone (rFSH) in patients with poor ovarian response undergoing in vitro fertilization/intracytoplasmic sperm injection with a gonadotropin-releasing hormone antagonist protocol. METHODS: This retrospective cohort study included 60 patients with poor ovarian response (30 received hp-hMG and 30 received rFSH) undergoing in vitro fertilization/intracytoplasmic sperm injection with a gonadotropin-releasing hormone antagonist protocol. Pregnancy-related outcomes, ovarian response, oocyte, and embryo parameters were compared between the 2 groups. Additionally, serum insulin-like growth factor-1 and insulin-like growth factor binding protein-1 levels on the day of oocyte retrieval were compared between the 2 groups. RESULTS: The 2 treatments resulted in comparable numbers of oocytes retrieved and embryos, comparable oocyte retrieval rate, mature oocyte rate, and fertilization rate, and also comparable clinical pregnancy rates, implantation rates, and miscarriage rate. However, hp-hMG led to statistically insignificant higher viable embryo rate (54.0% vs 44.8%; P = 0.174) and live birth rate per pregnancy (16.7% vs 10%) versus rFSH. Finally, statistically significantly higher serum insulin-like growth factor-1 level (178.53 [13.70] ng/mL vs 164.93 [12.17] ng/mL; P = 0.01) and statistically insignificantly lower serum insulin-like growth factor binding protein-1 level (19.53 [3.56] ng/mL vs the lower insulin-like growth factor binding protein-1 level SD is (2.76 [20.83] ng/mL; P > 0.05) on the day of oocyte retrieval were associated with hp-hMG versus rFSH. CONCLUSIONS: hp-HMG and rFSH did not lead to significantly different treatment outcomes in patients with poor ovarian response undergoing in vitro fertilization/intracytoplasmic sperm injection with a gonadotropin-releasing hormone antagonist protocol, although significantly higher serum insulin-like growth factor-1 level and insignificantly lower serum insulin-like growth factor binding protein-1 level on the day of oocyte retrieval associated with hp-HMG might suggest a beneficial endocrine environment. (Curr Ther Res Clin Exp. 2020; 81:XXX-XXX).

Metformin treatment alleviates polycystic ovary syndrome by decreasing the expression of MMP-2 and MMP-9 via H19/miR-29b-3p and AKT/mTOR/autophagy signaling pathways.

In this study, we aimed to investigate the molecular pathway(s) underlying the effect of metformin (MET) on the expression of matrix metalloproteinase (MMP)-2 and MMP-9. Real-time polymerase chain reaction, Western blot analysis, and gelatin zymography were used to assay the effects of MET on MMP and AMPK signaling pathways. In addition, HTOG cells were treated with miR-29b-3p/a scramble control, H19/a negative control, or MET/PBS to explore possible signaling pathway(s) underlying the inhibitory effect of MET on MMP-2/MMP-9. A rat model of polycystic ovary syndrome (PCOS) was also established to validate the molecular mechanism(s) of MET in vivo. The administration of MET suppressed the expression of MMP-9/MMP-2 and mTOR while increasing the expression of Akt and AMPK, indicating that MET reduced the expression of MMPs via the AMPK signaling pathway. Meanwhile, the H19/miR-29b-3p/MMP-9 and H19/miR-29b-3p/MMP-2 signaling pathways were implicated in PCOS, in which the interactions between H19/miR-29b-3p and MMP-9/MMP-2/miR-29b-3p were confirmed. Furthermore, the administration of MET suppressed the expression of H19 while elevating the expression of miR-29b-3p. And the role of MET in PCOS was also confirmed in vivo via examining the activity of H19 and AMPK signaling pathways in cell or serum samples collected from PCOS rats. MET exhibits a therapeutic effect in the treatment of PCOS by reducing the expression of MMPs.

Genetic variations and haplotypes in the annexin A5 gene are associated with the risk of recurrent pregnancy loss.

The expression of annexin A5 (ANXA5) was shown to affect the pathogenesis of recurrent pregnancy loss (RPL). In this study, the effects of two haplotypes, M1 and M2, on the transcription efficiency of ANXA5 promoter were explored. Correlation analysis was used to investigate the association between the single-nucleotide polymorphism haplotypes in ANXA5 promoter and the risk of RPL. And a luciferase reporter assay was carried out to study the effects of haplotypes M1 and M2 on the transcription efficiency of the ANXA5 promoter. To study the association between ANXA5 haplotypes and the risk of RPL, real-time polymerase chain reaction, western blot analysis, and immunohistochemistry assays were conducted to observe the expressions of ANXA5 messenger RNA (mRNA) and protein. Compared to M1 haplotype carriers, M2 haplotype carriers were associated with a higher risk of RPL. Additionally, compared to GATGTC haplotype carriers, GATGGC haplotype carriers were associated with a higher risk of RPL. Compared with RPL cases, the incidences of M2 haplotype were lower in both the population control and parous control cases. Furthermore, M2 carriers showed more significantly decreased activity of ANXA5 promoter compared to the carriers of other haplotypes, indicating that the haplotypes of ANXA5 promoter may be used as a potential biomarker to predict the prognosis of RPL. Moreover, the activity of ANXA5 as well as the mRNA/protein expression of ANXA5 was significantly downregulated in RPL patients, indicating that the M2 haplotype significantly increased the risk of RPL. Therefore, haplotype M2 increased the risk of RPL by inhibiting the expression of ANXA5.

Serum chemerin level in women with PCOS and its relation with the risk of spontaneous abortion.

BACKGROUND AND AIM: Insulin resistance (IR) was recognized as a risk factor for the occurrence of abortion in patients with polycystic ovary syndrome (PCOS). Chemerin was an adipokine which could induce IR and associated with reproductive process closely. However, few studies have inquired the relativity between chemerin and the occurrence of abortion in patients with PCOS. The aim of this study was to evaluate the relationship between serum chemerin and the occurrence of abortion in women with PCOS. METHODS: We recruited 198 women with PCOS to participate in our study. On the third day of menstrual cycle or a random day in women with amenorrhea, we obtained their venous blood and measured the fasting insulin, fasting plasma glucose, total cholesterol, high density lipoprotein cholesterol, triglyceride, chemerin, and hormones including FSH, E2, P, PRL, LH, and T. Additionally, BMI, HOMA-IR and LH/FSH of each subject were calculated. Finally, 58 of them were included in the study, in which 30 of them had normal pregnancy and the other 28 had an early miscarriage. We compared the biochemical characteristics between the normal pregnancy group and abortion group by independent-samples t test. RESULTS: In our study, those with a normal pregnancy had a lower level of BMI, FINs, HOMA-IR, and chemerin compared to abortion patients (p < .05). After adjusted for BMI, only chemerin was associated with the occurrence of abortion in PCOS patients (p < .05). CONCLUSIONS: Serum chemerin level is associated with the occurrence of abortion in patients with PCOS. Thus, serum chemerin may serve as a biomarker to identify pregnant women with PCOS who are at particular risk for later abortion, and who may benefit from prevention strategies.

Role of chemerin/CMKLR1 in the maintenance of early pregnancy.

Chemerin is a cytokine that attracts much attention in the reproductive process. This study aimed to explore the effects of chemerin and its receptor chemokine-like receptor 1 (CMKLR1) on the maintenance of early pregnancy. The expression levels of chemerin and CMKLR1 in the decidua tissues of 20 early normal pregnant women and 20 early spontaneous abortion women were examined by Western blot and real-time polymerase chain reaction analyses. CMKLR1 receptor antagonist (α-NETA) was then intrauterinely injected into normal pregnant mice model to assess its effect on the outcome of pregnancy and the phosphorylation rate of ERK1/2 in decidua tissues.We found that the expression level of chemerin in women who had experienced early spontaneous abortion was lower than in those who had experienced normal early pregnancy (P < 0.01); conversely, CMKLR1 expression was higher in the former than in the latter (P < 0.01). In a pregnant-mouse model, the embryo resorption rate of α-NETA group was higher than that in the negative control group (61.5% vs. 10.8%) (P < 0.001). Compared with the control group, ERK1/2 phosphorylation in decidua tissues decreased in the α-NETA-treated group (P < 0.01). These results suggested that the inhibition of the chemerin/CMKLR1 signaling pathway can lead to the abortion of mouse embryos, and that chemerin/CMKLR1 may play an important role in the maintenance of early pregnancy possibly by regulating ERK1/2 phosphorylation.

Serum chemerin level during the first trimester of pregnancy and the risk of gestational diabetes mellitus.

OBJECTIVE: To investigate the association between chemerin level in the first trimester of pregnancy and the risk of gestational diabetes mellitus. METHODS: The blood samples of 212 women at 8-12 weeks of gestation were collected. After screening for gestational diabetes mellitus (GDM), 19 women with GDM and 20 women randomly selected from 144 women with normal glucose tolerance (NGT) were included in the study. Blood samples were collected from these women. Triglycerides, glucose, total cholesterol, and HDL cholesterol, LDL cholesterol, insulin and chemerin were measured. Gestational weight gain and body mass index was assessed. RESULTS: Serum levels of chemerin were significantly elevated during late gestation, and the risk of GDM was positively associated with maternal serum chemerin in the first trimester. CONCLUSION: Serum chemerin level during the first trimester of pregnancy has the potential to predict risk of GDM.

Necrostatin-1 inhibits Hmgb1-IL-23/IL-17 pathway and attenuates cardiac ischemia reperfusion injury.

Ischemia reperfusion (IR) injury is a major issue in cardiac transplantation and inflammatory processes play a major role in myocardial IR injury. Necrostatin-1 (Nec-1) is a small molecule capable of inhibiting RIP1 kinase activity and attenuates inflammation-mediated tissue injury. In our study, hearts of C57Bl/6 mice were flushed and stored in cold Bretschneider solution for 8 h and then transplanted into syngeneic recipients. We found that Nec-1 decreased cardiomyocyte necrosis and recruitment of neutrophils and macrophages. Troponin T (TnT) production on 24 h after myocardial IR injury was reduced by Nec-1 administration. Cardiac output at 60 mmHg of afterload pressure was significantly increased in hearts with Nec-1 administration and the cardiac allograft survival in Nec-1-treated animals was significantly prolonged (MST = 90 days in IR + Nec-1 group, P < 0.05 as compared with IR group, MST = 83.5 days). Nec-1 treatment attenuated ROS generation and increased expression of NOS2 and COX-2. The expression of Hmgb1, IL-23, and IL-17A were also decreased with Nec-1 administration. Furthermore, the decreased TnT expression induced by Nec-1 was abrogated with exogenous Hmgb1 administration. In conclusion, Nec-1 played a protective role in cardiomyocyte IR injury, and this was associated with inhibited Hmgb1-IL-23/IL-17 pathway.

Isolation of proteorhodopsin-bearing bacterium JL-3 from fresh water and characterization of the proteorhodopsin.

Proteorhodopsins (PRs), light-driven proton pumps, constitute the largest family of the microbial rhodopsins. PRs are widely distributed in the oceanic environment and freshwater, but no bacteria with PRs have been isolated from freshwater so far. To facilitate isolation of the bacteria with PR genes, we constructed a vector system that can be used to clone potential PR genes and render color changes when overexpressed in Escherichia coli. Using this method, we successfully isolated a strain with PR gene from freshwater and identified it as Exiguobacterium sp. JL-3. The full length PR gene was then cloned using the SEFA PCR method. Protein sequence alignment showed that JL-3_PR shares high sequence identity (84-89%) with the PRs from Exiguobacterium strains, but low sequence identity (< 38%) with other PRs. Surprisingly, we could not detect any proton-pumping activity in the native JL-3 cells and protoplasts, but the recombinant JL-3_PR do pump protons when overexpressed in E. coli. Sequence analysis further revealed that the PRs from Exiguobacterium had an unusual lysine as the proton donor instead of the typical acidic residue. These data suggest that JL-3_PR is a sensory PR rather than a proton pump.

Crystallization and preliminary X-ray crystallographic analysis of a blue-light-absorbing proteorhodopsin.

Proteorhodopsins (PRs), seven-transmembrane chromoproteins with retinal as a chromophore, are light-driven proton pumps. To elucidate the light-driven proton-pumping mechanism of PRs, a pET28a vector containing the blue-light-absorbing proteorhodopsin (BPR) gene was constructed and the protein was overexpressed in Escherichia coli. The protein was purified by immobilized metal-ion affinity chromatography (IMAC). The purified BPR D97N mutant protein (BPR_D97N) was crystallized using the vapour-diffusion method. Preliminary X-ray diffraction data analysis showed that the crystal belonged to the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 161.6, b = 168.6, c = 64.7 Å. A complete data set was collected to 3.3 Å resolution using synchrotron radiation on beamline X06 of the Swiss Light Source (SLS). Molecular replacement was unsuccessful. To solve the structure of BPR_D97N by experimental phasing, selenomethionine-substituted protein crystals were prepared. These crystals diffracted to 3.0 Å resolution and a complete data set was collected on beamline BL17U of the Shanghai Synchrotron Radiation Facility (SSRF). Heavy-atom substructure determination and phasing by SAD clearly showed that the crystal contained five molecules in the asymmetric unit, with a V(M) of 3.26 Å(3) Da(-1) and a solvent content of 62.3%.