crescentin

Crescentin is a protein which is a bacterial relative of the intermediate filaments found in eukaryotic cells. Just as tubulins and actins, the other major cytoskeletal proteins, have prokaryotic homologs in, respectively, the FtsZ and MreB proteins, intermediate filaments are linked to the crescentin protein. Some of its homologs are erroneously labelled Chromosome segregation protein ParA. This protein family is found in Caulobacter and Methylobacterium.

==Role in cell shape== Crescentin was discovered in 2009 by Christine Jacobs-Wagner in Caulobacter crescentus (now vibrioides), an aquatic bacterium which uses its crescent-shaped cells for enhanced motility. The crescentin protein is located on the concave face of these cells and appears to be necessary for their shape, as mutants lacking the protein form rod-shaped cells. To influence the shape of the Caulobacter cells, the helices of crescentin filaments associate with the cytoplasmic side of the cell membrane on one lateral side of the cell. This induces a curved cell shape in younger cells, which are shorter than the helical pitch of crescentin, but induces a spiral shape in older, longer cells.