The DevS histidine kinase of Mycobacterium smegmatis contains tandem GAF domains (GAF-A and GAF-B) in its N-terminal sensory domain. The heme iron of DevS is in the ferrous state when purified and is resistant to autooxidation from a ferrous to a ferric state in the presence of O 2 . The redox property of the heme and the results of sequence comparison analysis indicate that DevS of M. smegmatis is more closely related to DosT of Mycobacterium tuberculosis than DevS of M. tuberculosis. The binding of O 2 to the deoxyferrous heme led to a decrease in the autokinase activity of DevS, whereas NO binding did not. The regulation of DevS autokinase activity in response to O 2 and NO was not observed in the DevS derivatives lacking its heme, indicating that the ligand-binding state of the heme plays an important role in the regulation of DevS kinase activity. The redox state of the quinone/quinol pool of the respiratory electron transport chain appears not to be implicated in the regulation of DevS activity. Neither cyclic GMP (cGMP) nor cAMP affected DevS autokinase activity, excluding the possibility that the cyclic nucleotides serve as the effector molecules to modulate DevS kinase activity. The three-dimensional structure of the putative GAF-B domain revealed that it has a GAF folding structure without cyclic nucleotide binding capacity.Mycobacterium smegmatis is a nonpathogenic and fast-growing mycobacterium whose adaptive response to a gradual decrease in oxygen tension and exposure to NO is similar to that of Mycobacterium tuberculosis (7). This adaptive capability of mycobacteria has been suggested to allow them to persist in a latent state in the immune-competent host, especially in the case of M. tuberculosis (14,24,35,52). The hypoxic conditions within granulomas, although this is controversial (1), and the NO synthesized by activated macrophages have been proposed to serve as possible signals for the transition of mycobacteria to the nonreplicating, latent state (35, 50, 52).The DevSR (DosSR) two-component system plays a crucial role in the adaptation of mycobacteria to hypoxic and NO conditions. Approximately 48 genes of M. tuberculosis were reported to be induced under hypoxic conditions, as well as on exposure to NO. The upregulation of these genes is mediated by the DevSR system (35, 38, 39, 52). The DevSR two-component system consists of the DevS histidine kinase (HK) and its cognate response regulator (39, 40). In addition to DevS, the DosT HK was found to cross talk with DevR and to be functional in M. tuberculosis (39,40). DevS and DosT show high sequence similarity to each other over the length of their primary structures. The N-terminal sensory domains of DevS and DosT contain two putative GAF domains. The first GAF domain (GAF-A) serves as a heme-binding domain, while the function of the second one (GAF-B) remains to be revealed (18,22,43,46). It was recently demonstrated that either the binding of O 2 to the ferrous form of hemes of both DevS and DosT or the oxidation of Fe 2ϩ within the heme to...
BackgroundIt has been reported that both chemical and physical surface patterns influence cellular behaviors, such as cell alignment and elongation. However, it still remains unclear how actin filament and microtubules (MTs) differentially respond to these patterns.ResultsWe examined the effects of chemical and physical patterns on cell elongation and alignment by observing actin filament and MTs of retinal pigment epithelium-1(RPE-1) cells, which were cultured on either fibronectin (FN)-line pattern (line width and spacing: 1 μm) or FN-coated 1 μm gratings with two different depths (0.35 or 1 μm). On the surface with either FN-line pattern or micrograting structure, the cell aspect ratios were at least two times higher than those on the surface with no pattern. Cell elongation on the gratings depended on the depth of the gratings. Cell elongation and alignment on both FN-line pattern and 1 μm gratings with 0.35 μm depth were perturbed either by inhibition of actin polymerization or MT depletion, while cell elongation and alignment on 1 μm gratings with 1 μm depth were perturbed only by MT depletion.ConclusionsOur results suggest that the contribution of actin filaments and MTs to the elongation and alignment of epithelial cells on microgratings depends on the groove depth of these gratings.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0187-8) contains supplementary material, which is available to authorized users.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.