title: The Ser/Thr protein kinase AfsK regulates polar growth and hyphal branching in the filamentous bacteria Streptomyces.
abstract: In cells that exhibit apical growth, mechanisms that regulate cell polarity are crucial for determination of cellular shape and for the adaptation of growth to intrinsic and extrinsic cues. Broadly conserved pathways control cell polarity in eukaryotes, but less is known about polarly growing prokaryotes. An evolutionarily ancient form of apical growth is found in the filamentous bacteria Streptomyces, and is directed by a polarisome-like complex involving the essential protein DivIVA. We report here that this bacterial polarization machinery is regulated by a eukaryotic-type Ser/Thr protein kinase, AfsK, which localizes to hyphal tips and phosphorylates DivIVA. During normal growth, AfsK regulates hyphal branching by modulating branch-site selection and some aspect of the underlying polarisome-splitting mechanism that controls branching of Streptomyces hyphae. Further, AfsK is activated by signals generated by the arrest of cell wall synthesis and directly communicates this to the polarisome by hyperphosphorylating DivIVA. Induction of high levels of DivIVA phosphorylation by using a constitutively active mutant AfsK causes disassembly of apical polarisomes, followed by establishment of multiple hyphal branches elsewhere in the cell, revealing a profound impact of this kinase on growth polarity. The function of AfsK is reminiscent of the phoshorylation of polarity proteins and polarisome components by Ser/Thr protein kinases in eukaryotes.
authors.affiliation: Department of Biology,  Lund University, 223 62 Lund,  Sweden.
authors.forename: Antje M
authors.initials: AM
authors.lastname: Hempel
authors.forename: Stuart
authors.initials: S
authors.lastname: Cantlay
authors.forename: Virginie
authors.initials: V
authors.lastname: Molle
authors.forename: Sheng-Bing
authors.initials: SB
authors.lastname: Wang
authors.forename: Mike J
authors.initials: MJ
authors.lastname: Naldrett
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Parker
authors.forename: David M
authors.initials: DM
authors.lastname: Richards
authors.forename: Yong-Gyun
authors.initials: YG
authors.lastname: Jung
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Buttner
authors.forename: Klas
authors.initials: K
authors.lastname: Flärdh
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D025301:Hyphae / Q000201:enzymology* / Q000254:growth & development*; D010457:Peptidoglycan / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology; D048372:Streptomyces coelicolor / Q000201:enzymology* / Q000254:growth & development*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D018797:Cell Cycle Proteins; C104636:DivIVA protein, bacteria; D010457:Peptidoglycan; D017346:Protein Serine-Threonine Kinases