Cytoskeletal proteins of actinobacteria

Abstract

Although bacteria are considered the simplest life forms, we are now slowly unraveling their cellular complexity. Surprisingly, not only do bacterial cells have a cytoskeleton but also the building blocks are not very different from the cytoskeleton that our own cells use to grow and divide. Nonetheless, despite important advances in our understanding of the basic physiology of certain bacterial models, little is known about Actinobacteria, an ancient group of Eubacteria. Here we review current knowledge on the cytoskeletal elements required for bacterial cell growth and cell division, focusing on actinobacterial genera such as Mycobacterium, Corynebacterium, and Streptomyces. These include some of the deadliest pathogens on earth but also some of the most prolific producers of antibiotics and antitumorals.

Figure 1

RodA is required for rod-shape maintenance of C. glutamicum. (a) In Actinobacteria, rodA is located within the conserved pkn cluster. (b) Prediction of transmembrane helices of RodA using TMHMM 2.0 software [93]. (c) Partial depletion of RodA generates coccoid cells (central) in the rod-shaped C. glutamicum (left), whereas a RodA overexpression results in club-shaped cells (right). M. Fiuza, unpublished results.

Figure 2

Cg0063 is phosphorylated in vitro by PknA and PknL in C. glutamicum. All four Ser/Thr Pkn kinases from C. glutamicum (PknA/B/L/G) and Cg0063 have been expressed and purified as described previously [105]. Then, Cg0063 was incubated alone or with the different Pkn kinases in the presence of [γ-³³P] ATP for 30 min. Samples were separated by SDS-PAGE electrophoresis and stained with Coomassie Blue (upper panel) or visualized by autoradiography (lower panel). PknA/B/L kinases exhibit an autophosphorylation activity, whereas Cg0063 is mostly phosphorylated by PknA and PknL. M. Fiuza, unpublished results.