4J7O

Structure of the N-terminal Repeat Domain of Rickettsia Sca2

Summary for 4J7O

• Entry DOI: 10.2210/pdb4j7o/pdb
• Descriptor: Putative surface cell antigen sca2, GLYCEROL (3 entities in total)
• Functional Keywords: helical repeat, actin nucleation, actin, cell invasion
• Biological source: Rickettsia conorii
• Cellular location: Cell outer membrane (By similarity): Q92JF7
• Total number of polymer chains: 1
• Total formula weight: 42484.53

Authors

Madasu, Y.,Dominguez, R. (deposition date: 2013-02-13, release date: 2013-07-03, Last modification date: 2024-02-28)

Primary citation

Madasu, Y.,Suarez, C.,Kast, D.J.,Kovar, D.R.,Dominguez, R.
Rickettsia Sca2 has evolved formin-like activity through a different molecular mechanism.
Proc.Natl.Acad.Sci.USA, 110:E2677-E2686, 2013

PubMed Abstract: Sca2 (surface cell antigen 2) is the only bacterial protein known to promote both actin filament nucleation and profilin-dependent elongation, mimicking eukaryotic formins to assemble actin comet tails for Rickettsia motility. We show that Sca2's functional mimicry of formins is achieved through a unique mechanism. Unlike formins, Sca2 is monomeric, but has N- and C-terminal repeat domains (NRD and CRD) that interact with each other for processive barbed-end elongation. The crystal structure of NRD reveals a previously undescribed fold, consisting of helix-loop-helix repeats arranged into an overall crescent shape. CRD is predicted to share this fold and might form together with NRD, a doughnut-shaped formin-like structure. In between NRD and CRD, proline-rich sequences mediate the incorporation of profilin-actin for elongation, and WASP-homology 2 (WH2) domains recruit actin monomers for nucleation. Sca2's α-helical fold is unusual among Gram-negative autotransporters, which overwhelmingly fold as β-solenoids. Rickettsia has therefore "rediscovered" formin-like actin nucleation and elongation.

PubMed: 23818602
DOI: 10.1073/pnas.1307235110

Experimental method

X-RAY DIFFRACTION (2.175 Å)