title: Biochemical and biological properties of cortexillin III, a component of Dictyostelium DGAP1-cortexillin complexes.
abstract: Cortexillins I-III are members of the α-actinin/spectrin subfamily of Dictyostelium calponin homology proteins. Unlike recombinant cortexillins I and II, which form homodimers as well as heterodimers in vitro, we find that recombinant cortexillin III is an unstable monomer but forms more stable heterodimers when coexpressed in Escherichia coli with cortexillin I or II. Expressed cortexillin III also forms heterodimers with both cortexillin I and II in vivo, and the heterodimers complex in vivo with DGAP1, a Dictyostelium GAP protein. Binding of cortexillin III to DGAP1 requires the presence of either cortexillin I or II; that is, cortexillin III binds to DGAP1 only as a heterodimer, and the heterodimers form in vivo in the absence of DGAP1. Expressed cortexillin III colocalizes with cortexillins I and II in the cortex of vegetative amoebae, the leading edge of motile cells, and the cleavage furrow of dividing cells. Colocalization of cortexillin III and F-actin may require the heterodimer/DGAP1 complex. Functionally, cortexillin III may be a negative regulator of cell growth, cytokinesis, pinocytosis, and phagocytosis, as all are enhanced in cortexillin III-null cells.
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Xiong
authors.initials: X
authors.lastname: Liu
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Shi
authors.initials: S
authors.lastname: Shu
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Shuhua
authors.initials: S
authors.lastname: Yu
authors.affiliation: Biochemistry Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Duck-Yeon
authors.initials: DY
authors.lastname: Lee
authors.affiliation: Biophysics Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Piszczek
authors.affiliation: Proteomics Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Marjan
authors.initials: M
authors.lastname: Gucek
authors.affiliation: Proteomics Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Wang
authors.affiliation: Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892 edk@nih.gov.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Korn
mesh_terms: D000199:Actins / Q000737:chemistry; D000818:Animals; D004023:Dictyostelium / Q000166:cytology / Q000378:metabolism*; D008840:Microfilament Proteins / Q000737:chemistry* / Q000378:metabolism; D046912:Multiprotein Complexes / Q000737:chemistry; D010641:Phenotype; D011485:Protein Binding; D055503:Protein Multimerization; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism; D061987:Sf9 Cells; D018411:Spodoptera
chemical_list: D000199:Actins; D008840:Microfilament Proteins; D046912:Multiprotein Complexes; D015800:Protozoan Proteins