Abhrajyoti Ghosh

Publications (19) View all

• Article: Insights into FlaI Functions in Archaeal Motor Assembly and Motility from Structures, Conformations, and Genetics.

  Sophia Reindl, Abhrajyoti Ghosh, Gareth J Williams, Kerstin Lassak, Tomasz Neiner, Anna-Lena Henche, Sonja-Verena Albers, John A Tainer
  [show abstract] [hide abstract]
  ABSTRACT: Superfamily ATPases in type IV pili, type 2 secretion, and archaella (formerly archaeal flagella) employ similar sequences for distinct biological processes. Here, we structurally and functionally characterize prototypical superfamily ATPase FlaI in Sulfolobus acidocaldarius, showing FlaI activities in archaeal swimming-organelle assembly and movement. X-ray scattering data of FlaI in solution and crystal structures with and without nucleotide reveal a hexameric crown assembly with key cross-subunit interactions. Rigid building blocks form between N-terminal domains (points) and neighboring subunit C-terminal domains (crown ring). Upon nucleotide binding, these six cross-subunit blocks move with respect to each other and distinctly from secretion and pilus ATPases. Crown interactions and conformations regulate assembly, motility, and force direction via a basic-clamp switching mechanism driving conformational changes between stable, backbone-interconnected moving blocks. Collective structural and mutational results identify in vivo functional components for assembly and motility, phosphate-triggered rearrangements by ATP hydrolysis, and molecular predictors for distinct ATPase superfamily functions.
  Molecular cell 02/2013; · 14.61 Impact Factor
• Article: Diversity, assembly and regulation of archaeal type IV pili-like and non-type-IV pili-like surface structures.

  Kerstin Lassak, Abhrajyoti Ghosh, Sonja-Verena Albers
  [show abstract] [hide abstract]
  ABSTRACT: Archaea have evolved fascinating surface structures allowing rapid adaptation to changing environments. The archaeal surface appendages display such diverse biological roles as motility, adhesion, biofilm formation, exchange of genetic material and species-specific interactions and, in turn, increase fitness of the cells. Intriguingly, despite sharing the same functions with their bacterial counterparts, the assembly mechanism of many archaeal surface structures is rather related to assembly of bacterial type IV pili. This review summarizes our state-of-the-art knowledge about unique structural and biochemical properties of archaeal surface appendages with a particular focus on archaeal type IV pili-like structures. The latter comprise not only widely distributed archaella (formerly known as archaeal flagella), but also different highly specialized archaeal pili, which are often restricted to certain species. Recent findings regarding assembly mechanisms, structural aspects and physiological roles of these type IV pili-like structures will be discussed in detail. Recently, first regulatory proteins involved in transition from both planktonic to sessile lifestyle and in assembly of archaella were identified. To conclude, we provide novel insights into regulatory mechanisms underlying the assembly of archaeal surface structures.
  Research in Microbiology 11/2012; · 2.76 Impact Factor
• Article: FlaX, a unique component of the crenarchaeal archaellum, forms oligomeric ring-shaped structures and interacts with the motor ATPase FlaI.

  Ankan Banerjee, Abhrajyoti Ghosh, Deryk J Miller, Joerg Kahnt, Janet Vonck, Sonja-Verena Albers
  [show abstract] [hide abstract]
  ABSTRACT: Archaella are the archaeal motility structure, which are structurally similar to gram-negative bacterial type IV pili but functionally resemble bacterial flagella. Structural and biochemical data of archaellum subunits are missing. FlaX, a conserved subunit in crenarchaeal archaella, formed high molecular weight complexes that adapted a ring-like structure with an approximate diameter of 30 nm. The C-terminus of FlaX was not only involved in the oligomerization, but also essential for FlaX interaction with FlaI, the bifunctional ATPase which is involved in assembly and rotation of the archaellum. This study gives first insights in the assembly apparatus of archaella.
  Journal of Biological Chemistry 11/2012; · 4.77 Impact Factor
• Article: Structure and function of the adhesive type IV pilus of Sulfolobus acidocaldarius.

  Anna-Lena Henche, Abhrajyoti Ghosh, Xiong Yu, Torsten Jeske, Edward Egelman, Sonja-Verena Albers
  [show abstract] [hide abstract]
  ABSTRACT: Archaea display a variety of type IV pili on their surface and employ them in different physiological functions. In the crenarchaeon Sulfolobus acidocaldarius the most abundant surface structure is the aap pilus (archaeal adhesive pilus). The construction of in frame deletions of the aap genes revealed that all the five genes (aapA, aapX, aapE, aapF, aapB) are indispensible for assembly of the pilus and an impact on surface motility and biofilm formation was observed. Our analyses revealed that there exists a regulatory cross-talk between the expression of aap genes and archaella (formerly archaeal flagella) genes during different growth phases. The structure of the aap pilus is entirely different from the known bacterial type IV pili as well as other archaeal type IV pili. An aap pilus displayed 3 stranded helices where there is a rotation per subunit of ∼ 138° and a rise per subunit of ∼ 5.7 Å. The filaments have a diameter of ∼ 110 Å and the resolution was judged to be ∼ 9 Å. We concluded that small changes in sequence might be amplified by large changes in higher-order packing. Our finding of an extraordinary stability of aap pili possibly represents an adaptation to harsh environments that S. acidocaldarius encounters.
  Environmental Microbiology 09/2012; · 5.84 Impact Factor
• Article: Molecular analysis of the crenarchaeal flagellum.

  Kerstin Lassak, Tomasz Neiner, Abhrajyoti Ghosh, Andreas Klingl, Reinhard Wirth, Sonja-Verena Albers
  [show abstract] [hide abstract]
  ABSTRACT: The ability to move towards favourable conditions provides fundamental advantages to organisms. Interestingly, flagella as motility structures evolved independently in the bacterial and the archaeal kingdom. Whereas bacterial flagella have been intensively studied, our knowledge regarding the archaeal counterpart is mostly restricted to Euryarchaeota rather than crenarchaeal flagella. We therefore investigated the flagellar assembly system of the crenarchaeal model organism Sulfolobus acidocaldarius in vivo. Promoter studies and qRT-PCR analyses of the flagella gene cluster provided evidence that the expression of the fla genes was induced by tryptone starvation. Moreover, we confirmed presence of a secondary fla promoter within the flaB gene that regulates the transcription of downstream genes flaX-J. Markerless in-frame deletions for all fla genes encoded in the fla gene cluster were constructed. Western blot analysis of all fla deletion strains suggested hierarchical protein interactions during the archaeal flagella assembly. Moreover, functional analysis by thermomicroscopy revealed non-motile cells for each of the mutant strains. Electron micrographs demonstrated that lack of motility coincided with the loss of flagellar assembly. Thus we demonstrated that all seven fla genes are essential for crenarchaeal flagellum assembly and function.
  Molecular Microbiology 11/2011; 83(1):110-24. · 5.01 Impact Factor