Crystal structure of Bacillus anthracis virulence regulator AtxA and effects of phosphorylated histidines on multimerization and activity. Issue 3 (30th December 2014)

• Record Type: Journal Article
• Authors: Hammerstrom, Troy G.; Horton, Lori B.; Swick, Michelle C.; Joachimiak, Andrzej; Osipiuk, Jerzy; Koehler, Theresa M.
• Is Part Of: Molecular microbiology. Volume 95:Issue 3(2015)
• Page Start: 426
• Page End: 441
• Publication Date: 2014-12-30
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.12867
• Languages: English
• ISSNs: 0950-382X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>The <italic>B</italic><italic>acillus anthracis</italic> virulence regulator AtxA controls transcription of the anthrax toxin genes and capsule biosynthetic operon. AtxA activity is elevated during growth in media containing glucose and CO<sub>2</sub>/bicarbonate, and there is a positive correlation between the CO<sub>2</sub>/bicarbonate signal, AtxA activity and homomultimerization. AtxA activity is also affected by phosphorylation at specific histidines. We show that AtxA crystallizes as a dimer. Distinct folds associated with predicted DNA‐binding domains (HTH1 and HTH2) and phosphoenolpyruvate: carbohydrate phosphotransferase system‐regulated domains (PRD1 and PRD2) are apparent. We tested AtxA variants containing single and double phosphomimetic (His→Asp) and phosphoablative (His→Ala) amino acid changes for activity in <italic>B</italic><italic>. anthracis</italic> cultures and for protein–protein interactions in cell lysates. Reduced activity of AtxA H199A, lack of multimerization and activity of AtxAH379D variants, and predicted structural changes associated with phosphorylation support a model for control of AtxA function. We propose that (i) in the AtxA dimer, phosphorylation of H199 in PRD1 affects HTH2 positioning, influencing DNA‐binding; and (ii) phosphorylation of H379 in PRD2 disrupts dimer formation. The AtxA structure is the first reported high‐resolution full‐length structure of a PRD‐containing regulator, and can serve as a model for proteins of this family, especially those that link virulence to bacterial metabolism.</p> </abstract>