Solubilisation of the armadillo-repeat protein β-catenin using a zwitterionic detergent allows resolution of phosphorylated forms by 2DE

Sphingosine kinase (SPHK) is a key enzyme catalysing the formation of sphingosine 1-phosphate (SPP), a lipid messenger that is implicated in the regulation of a wide variety of important cellular events acting through intracellular, as well as extracellular, mechanisms. However, the molecular mechanism of intracellular actions of SPP remains unclear. Here, we have identified δ-catenin/NPRAP (neural plakophilin-related armadillo repeat protein) as a potential binding partner for SPHK1 by yeast two-hybrid screening. From co-immunoprecipitation analyses, the C-terminal portion of δ-catenin/NPRAP containing the seventh to tenth armadillo repeats was found to be required for interaction with SPHK1. Endogenous δ-catenin/NPRAP was co-localized with endogenous SPHK1 and transfected δ-catenin/NPRAP was co-localized with transfected SPHK1 in dissociated rat hippocampal neurons. MDCK (Madin–Darby canine kidney) cells stably expressing δ-catenin/NPRAP contained elevated levels of intracellular SPP. In a purified system δ-catenin/NPRAP stimulated SPHK1 in a dose-dependent manner. Furthermore, δ-catenin/NPRAP-induced increased cell motility in MDCK cells was completely inhibited by dimethylsphingosine, a specific inhibitor of SPHK1. These results strongly suggest that at least some of δ-catenin/NPRAP functions, including increased cell motility, are mediated by an SPHK–SPP signalling pathway.

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F-Actin Organization and Pollen Tube Tip Growth in Arabidopsis Are Dependent on the Gametophyte-Specific Armadillo Repeat Protein ARO1

The Plant Cell ◽

10.1105/tpc.108.061028 ◽

2008 ◽

Vol 20 (10) ◽

pp. 2798-2814 ◽

Cited By ~ 27

Author(s):

Marina Gebert ◽

Thomas Dresselhaus ◽

Stefanie Sprunck

Keyword(s):

Pollen Tube ◽

Tip Growth ◽

Repeat Protein ◽

Actin Organization ◽

Armadillo Repeat

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Chlamydomonas ARMC2/PF27 is an obligate cargo adapter for IFT of radial spokes

10.1101/2021.10.31.466660 ◽

2021 ◽

Author(s):

Karl F Lechtreck ◽

Yi Liu ◽

Jin Dai ◽

Rama Alkhofash ◽

Jack Butler ◽

...

Keyword(s):

Lung Function ◽

Male Infertility ◽

Cell Body ◽

Intraflagellar Transport ◽

Proximal Region ◽

Repeat Protein ◽

Radial Spokes ◽

Armadillo Repeat ◽

Dynein Arms

Intraflagellar transport (IFT) carries proteins into flagella but how IFT trains interact with the large number of diverse proteins required to assemble flagella remains largely unknown. Here, we show that IFT of radial spokes in Chlamydomonas requires ARMC2/PF27, a conserved armadillo repeat protein associated with male infertility and reduced lung function. Chlamydomonas ARMC2 was highly enriched in growing flagella and tagged ARMC2 and the spoke protein RSP3 comigrated on anterograde trains. In contrast, a cargo and an adapter of inner and outer dynein arms moved independently of ARMC2, indicating that unrelated cargoes distribute stochastically onto the IFT trains. After concomitant unloading at the flagellar tip, RSP3 attached to the axoneme whereas ARMC2 diffused back to the cell body. In armc2/pf27 mutants, IFT of radial spokes was abolished and the presence of radial spokes was limited to the proximal region of flagella. We conclude that ARMC2 is a cargo adapter required for IFT of radial spokes to ensure their assembly along flagella. ARMC2 belongs to a growing class of cargo-specific adapters that enable flagellar transport of preassembled axonemal substructures by IFT.

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Peptide binding affinity redistributes preassembled repeat protein fragments

Biological Chemistry ◽

10.1515/hsz-2018-0355 ◽

2019 ◽

Vol 400 (3) ◽

pp. 395-404

Author(s):

Erich Michel ◽

Andreas Plückthun ◽

Oliver Zerbe

Keyword(s):

Protein Complexes ◽

Population Analysis ◽

Variable Number ◽

Protein Fragments ◽

Repeat Protein ◽

Target Peptide ◽

Repeat Proteins ◽

Armadillo Repeat ◽

Conformational Rearrangements ◽

Peptide Binding Affinity

Abstract Designed armadillo repeat proteins (dArmRPs) are modular peptide binders composed of N- and C-terminal capping repeats Y and A and a variable number of internal modules M that each specifically recognize two amino acids of the target peptide. Complementary fragments of dArmRPs obtained by splitting the protein between helices H1 and H2 of an internal module show conditional and specific assembly only in the presence of a target peptide (Michel, E., Plückthun, A., and Zerbe, O. (2018). Peptide-guided assembly of repeat protein fragments. Angew. Chem. Int. Ed. 57, 4576–4579). Here, we investigate dArmRP fragments that already spontaneously assemble with high affinity, e.g. those obtained from splits between entire modules or between helices H2 and H3. We find that the interaction of the peptide with the assembled fragments induces distal conformational rearrangements that suggest an induced fit on a global protein level. A population analysis of an equimolar mixture of an N-terminal and three C-terminal fragments with various affinities for the target peptide revealed predominant assembly of the weakest peptide binder. However, adding a target peptide to this mixture altered the population of the protein complexes such that the combination with the highest affinity for the peptide increased and becomes predominant when adding excess of peptide, highlighting the feasibility of peptide-induced enrichment of best binders from inter-modular fragment mixtures.

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