Structural characterization of DNA-binding domain of essential mammalian protein TTF 1.

Transcription Termination Factor 1 (TTF1) is a multifunctional mammalian protein with vital roles in various cellular processes, including Pol I-mediated transcription initiation and termination, pre-rRNA processing, chromatin remodelling, DNA damage repair, and polar replication fork arrest. It comprises two distinct functional regions; the N-terminal regulatory region (1-445 aa), and the C-terminal catalytic region (445-859 aa). The Myb domain located at the C-terminal region is a conserved DNA binding domain spanning from 550 to 732 aa (183 residues). Despite its critical role in various cellular processes, the physical structure of TTF1 remains unsolved. Attempts to purify the functional TTF1 protein have been unsuccessful till date. Therefore, we focused on characterizing the Myb domain of this essential protein. We started with predicting a 3-D model of the Myb domain using homology modelling, and ab-initio method. We then determined its stability through MD simulation in an explicit solvent. The model predicted is highly stable, which stabilizes at 200ns. To experimentally validate the computational model, we cloned and expressed the codon optimized Myb domain into a bacterial expression vector and purified the protein to homogeneity. Further, characterization of the protein shows that, Myb domain is predominantly helical (65%) and is alone sufficient to bind the Sal Box DNA. This is the first-ever study to report a complete in silico model of the Myb domain, which is physically characterized. The above study will pave the way towards solving the atomic structure of this essential mammalian protein.

Linezolid-induced dental hyperpigmentation in an adult male being treated for an ulcer caused by atypical mycobacteria.

Mycobacteria are intrinsically resistant to most antibiotics as a result of multiple mechanisms. Linezolid, a member of the oxazolidinones, is a newer class of synthetic antimicrobials which is frequently used to treat mycobacteria. Here, we report a case of a patient with an ulcer on the right arm, caused by atypical mycobacteria, who presented with discoloration of both the upper and lower teeth after being treated with linezolid for a period of 2 months. On detailed evaluation, the patient was found to have linezolid-induced dental hyperpigmentation. This is the first case reported ever in an adult having linezolid-induced dental hyperpigmentation.

Comparison of Induced Sputum and Bronchoalveolar Lavage Fluid Examination in the Diagnosis of Sputum Negative Pulmonary Tuberculosis.

BACKGROUND: Tuberculosis (TB) is one of the common infections in the world, especially in developing countries like India. Therefore, early diagnosis is important. This study was undertaken to compare the yield of sputum, induction with bronchoalveolar lavage (BAL) in smear-negative suspected pulmonary TB patients in a tertiary care hospital in Agra. METHODS: Fifty patients were included in the study. In all patients, induced sputum, fibreoptic bronchoscopy and BAL fluid were subjected to diagnostic testing. RESULTS: On acid-fast smear examination, induced sputum and BAL fluid tested positive in 27/50 and 25/50 patients, respectively with a sensitivity of 83.3% and 90% respectively (p<0.0001). On comparing sputum induction versus BAL on culture, 30 patients were positive by sputum induction and 27 patients were positive on BAL fluid, with the sensitivity of 85.7% and 77.1%, respectively. The results showed that the sputum induction showed a significantly higher yield than that of BAL fluid (p=0.0013). CONCLUSION: Sputum induction offers an alternative approach in the diagnosis of smear-negative suspected pulmonary TB patients and would enhance sensitivity for the diagnosis of TB.