The VapBC1 toxin-antitoxin complex from Mycobacterium tuberculosis: purification, crystallization and X-ray diffraction analysis

• Published in: Acta crystallographica. Section F, Structural biology communications Structural biology communications, 2016-06, Vol.72 (6), p.485-489
• Main Authors: Lu, Zuokun, Wang, Han, Zhang, Aili, Tan, Yusheng
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antitoxins - chemistry; Bacterial Proteins - chemistry; Bacterial Toxins - chemistry; Crystallization; Crystallography, X-Ray - methods; drug target; Mycobacterium tuberculosis; Mycobacterium tuberculosis - chemistry; Research Communications; toxin-antitoxin system; VapBC
• ISSN: 2053-230X; 2053-230X
• DOI: 10.1107/S2053230X16007603

Mycobacterium tuberculosis, a major human pathogen, encodes at least 88 toxin–antitoxin (TA) systems. Remarkably, more than half of these modules belong to the VapBC family. Under normal growth conditions, the toxicity of the toxin VapC is neutralized by the protein antitoxin VapB. When bacteria face an unfavourable environment, the antitoxin is degraded and the free toxin VapC targets important cellular processes in order to inhibit cell growth. TA systems function in many biological processes, such as in the stringent response, in biofilm formation and in drug tolerance. To explore the structure of the VapBC1 complex, the toxin VapC1 and the antitoxin VapB1 were separately cloned, co‐expressed and crystallized. The best crystal was obtained using a crystallization solution consisting of optimized solution with commercial sparse‐matrix screen solutions as additives. The crystal diffracted to a resolution of 2.7 Å and belonged to space group P21, with unit‐cell parameters a = 59.3, b = 106.7, c = 250.0 Å, β = 93.75°. Bacterial VapBC modules belong to the type II toxin–antitoxin systems, which function in many important biological processes, such as the stringent response and drug tolerance. The toxin VapC1 and the cognate antitoxin VapB1 from M. tuberculosis were separately cloned and co‐expressed in E. coli BL21(DE3) cells. Diffraction‐quality crystals were obtained by using commercial sparse‐matrix screen solutions as additives.