BINDING OF AN ARM REPEAT PROTEIN TO THE KINASE DOMAIN OF THE S-LOCUS RECEPTOR KINASE

Screening of a yeast two-hybrid library for proteins that interact wit h the kinase domain of an S-locus receptor kinase (SRK) resulted in th e isolation of a plant protein called ARC1 (Arm Repeat Containing), Th is interaction was mediated by the C-terminal region of ARC1 in which five arm repeat units were identified, Using the yeast two-hybrid syst em and in vitro binding assays, ARC1 was found to interact specificall y with the kinase domains from SRK-910 and SRK-A14 but failed to inter act with kinase domains from two different Arabidopsis receptor-like k inases, In addition, treatment with a protein phosphatase or the use o f a kinase-inactive mutant reduced or abolished the binding of ARC1 to the SRK-910 kinase domain, indicating that the interaction was phosph orylation dependent, Lastly, RNA blot analysis revealed that the expre ssion of ARC1 is restricted to the stigma, the site of the self-incomp atibility response.