Identification of New Specificity Determinants in Bacterial Purine Nucleobase Transporters based on an Ancestral Sequence Reconstruction Approach.

The relation of sequence with specificity in membrane transporters is challenging to explore. Most relevant studies until now rely on comparisons of present-day homologs. In this work, we study a set of closely related transporters by employing an evolutionary, ancestral-reconstruction approach and reveal unexpected new specificity determinants. We analyze a monophyletic group represented by the xanthine-specific XanQ of Escherichia coli in the Nucleobase-Ascorbate Transporter/Nucleobase-Cation Symporter-2 (NAT/NCS2) family. We reconstructed AncXanQ, the putative common ancestor of this clade, expressed it in E. coli K-12, and found that, in contrast to XanQ, it encodes a high-affinity permease for both xanthine and guanine, which also recognizes adenine, hypoxanthine, and a range of analogs. AncXanQ conserves all binding-site residues of XanQ and differs substantially in only five intramembrane residues outside the binding site. We subjected both homologs to rationally designed mutagenesis and present evidence that these five residues are linked with the specificity change. In particular, we reveal Ser377 of XanQ (Gly in AncXanQ) as a major determinant. Replacement of this Ser with Gly enlarges the specificity of XanQ towards an AncXanQ-phenotype. The ortholog from Neisseria meningitidis retaining Gly at this position is also a xanthine/guanine transporter with extended substrate profile like AncXanQ. Molecular Dynamics shows that the S377G replacement tilts transmembrane helix 12 resulting in rearrangement of Phe376 relative to Phe94 in the XanQ binding pocket. This effect may rationalize the enlarged specificity. On the other hand, the specificity effect of S377G can be masked by G27S or other mutations through epistatic interactions.

Providing care to patients with COVID-19 in a reference hospital: health care staff intentional behavior and factors that affect it.

OBJECTIVE: The investigation of intentional behavior of hospital staff to care for COVID-19 patients and the study of the factors that influences it. METHOD: This is a cross-sectional study, of 261 physicians and nurses working in a COVID-19 reference hospital. Data were collected by an anonymous questionnaire including demographic and professional characteristics and a scale measuring behavioral intention based on the Theory of Planned Behavior of Ajzen. Statistical analysis was performed by SPSS 21. RESULTS: Mean age of participants was 40.8 years old, while most of them were nurses (75.7%). Behavioral intention mean score was 18.2 (5-21), which shows high intention to care for COVID-19 patients. Bivariate analysis between independent variables showed that behavioral intention mean score was higher for those that had cared for COVID-19 patients and those that did not (19.0% vs. 16.7%, p < 0.001). Multivariate linear regression analysis identified that increased subjective norms (the perceived social pressure to perform or not the behavior) score was associated with increased behavioral intention score (p < 0.001). Also, participants that provided care for COVID-19 patients had higher behavioral intention score (p < 0.001). CONCLUSION: Healthcare staff, that cared for COVID-19 patients had high behavioral intention to continue caring for them. This finding could be used to inform policies and training for staff that will be employed in COVID-19 units.

Serum Hyaluronic Acid Levels Are Altered in Acute Leukemia Patients: Potential Prognostic Implications.

BACKGROUND: Studies on the serum concentration of hyaluronic acid (HA) in newly diagnosed patients with acute myeloid leukemia (AML), B-acute lymphoblastic leukemia (B-ALL), and mantle-cell lymphoma (MCL) are scarce. In this study, we focused on investigating whether HA could serve as a possible prognostic marker in patients with AML, B-ALL, and MCL. METHODS: The serum concentration of HA was measured in a total of 51 patients with newly diagnosed AML, B-ALL, and MCL. Venous blood was collected 1 day before the initiation of chemotherapy (D0), on day 16 of the first cycle of chemotherapy (D16), and on D30. RESULTS: The serum HA concentration on D0 in patients with AML, B-ALL, and MCL was higher than in the control group. For all types of hematological malignancy, on D0, serum HA values of nonsurvivors were higher than in survivors. Moreover, patients in relapse had higher levels of serum HA than patients in remission. A strong positive correlation between serum HA and ferritin, ß2-microglobulin, and lactate dehydrogenase was found. CONCLUSION: Serum HA may serve as a possible prognostic marker for AML, B-ALL, and MCL patients, especially on D0. Prospective case-control studies on larger populations may provide further information.

Cardiovascular Risk and Serum Hyaluronic Acid: A Preliminary Study in a Healthy Population of Low/Intermediate Risk.

BACKGROUND: Hyaluronic acid (HA) has been found to be an important trigger of atherosclerosis. In this study, we investigate the possible association of serum HA with cardiovascular disease risk in a population of low/intermediate risk for cardiovascular events. METHODS: We enrolled 200 subjects with low/intermediate risk for developing cardiovascular disease. High specific C-reactive protein (hsCRP) was used as an indicator of preclinical atherosclerosis. The Framingham score was used to calculate the cardiovascular risk. RESULTS: Participants with dyslipidemia had significantly higher levels of serum HA than those without dyslipidemia (t-test, P = 0.05), higher levels of hsCRP (Kruskal-Wallis test, P = 0.04), and higher cardiovascular risk according to the Framingham score (Kruskal-Wallis test, P = 0.05). Serum HA concentration correlated significantly with the Framingham score for risk for coronary heart disease over the next 10 years (Spearman r = 0.152, P = 0.02). Diabetic volunteers had significantly higher HA than those without diabetes (t-test, P = 0.02). Participants with metabolic syndrome had higher serum HA levels and higher hsCRP (Kruskal-Wallis test, P = 0.01) compared to volunteers without metabolic syndrome (t-test, P = 0.03). CONCLUSIONS: Serum HA should be explored as an early marker of atheromatosis and cardiovascular risk.