Study On The Structure And Function Of Mycobacterium Tuberculosis Proteins Rv3094c And Rv3855

Tuberculosis（TB）is caused by Mycobacterium tuberculosis（M.tb）,and pulmonary infection is the most common.Tuberculosis has high mobility and mortality.In the post antibiotic era,the emergence of a large number of drugresistant bacteria reduces the efficacy of anti-tuberculosis drugs,therefore,tuberculosis patients are suffering from both disease and long-term chemotherapy.Among the existing anti-tuberculosis drugs,isoniazid（INH）,rifampicin（RFP）,ethambutol,pyrazinamide（PZA）and streptomycin are classified as first-line anti tuberculosis drugs,and the rest are all second-line anti tuberculosis drugs.When the first-line drugs are ineffective against bacterial infection,the second-line drugs will play a role.With the increase of multidrug-resistant（MDR）and extensively drug-resistant（XDR）M.tb,secondline drugs such as ethionamide（ETH）have become one of the most commonly used and effective antituberculotics in the treatment of drug-resistant tuberculosis.Previous studies on ETH mainly focused on metabolism,and research on its activation and resistance mechanisms in M.tb has been strengthened in recent years.In this study,the crystal structures of Apo-Rv3094 c,Rv3094c/FMN binary complex and Rv3094c/FMN/ETH ternary complex were analyzed by structural biology methods.Meanwhile,the crystal structures of Rv3855 and its target gene DNA complex were studied by the same method.The Apo form of Rv3094 c consists of N-terminal-,C-terminal and intermediate domain.In the Apo form,F136 and F221 play a key role.Among them,F136 is the main residue involved in the formation of FMN binding pocket.That is to say,when the prosthetic group FMN binds to Rv3094 c,the side chain of F136 swings outward to form the pocket accommodating FMN.In addition,F221 mediated the reaction between flavin ring of FMN and ETH.Sequence alignment between Rv3094 c and HPAMO showed that F221 was strictly conserved（corresponding to F266 in HPAMO）,but the position of side chain of F221 did not change significantly before and after ETH binding.The catalytic activity of wild-type and mutant protein of Rv3094 c to ETH showed that the change of specific residues in FMN pocket（W80A,S138 A,W174A,W179 A and H351R）could significantly reduce the catalytic activity of ETH.Based on structural analysis and functional study,we finally proposed the mechanism of sulfur oxidation of ETH by Rv3094 c.In addition,we are also pushing forward the structural biology research of Rv3855 and target gene DNA complex.In this study,we first analyzed the crystal structure of ETH activator Rv3094 c and substrate ETH.Based on the study of structure and function,we proposed the mechanism model of ETH sulfur oxidation,which laying an important foundation for further understanding the activation process and drug resistance mechanism of ETH in M.tb and has very important practical significance.