Interaction of Arabidopsis kinesin-like calmodulin-binding protein with tubulin subunits: modulation by Ca(2+)-calmodulin.
Kinesin-like calmodulin-binding protein (KCBP) is a recently identified novel kinesin-like protein that appears to be unique to and ubiquitous in plants. KCBP is distinct from all other known KLPs in having a calmodulin-binding domain adjacent to its motor domain. We have used different regions of KCBP to study its interaction with tubulin subunits and the regulation of this interaction by Ca(2+)-calmodulin. The results show that the carboxy-terminal part of the KCBP, with or without calmodulin-binding domain, binds to tubulin subunits and this binding is sensitive to nucleotides. In the presence of Ca(2+)-calmodulin the motor with calmodulin-binding domain does not bind to tubulin. This Ca(2+)-calmodulin modulation is abolished in the presence of antibodies specific to the calmodulin-binding domain of KCBP. Similar binding studies with the carboxy-terminal part of KCBP lacking the calmodulin-binding domain show no effect of Ca(2+)-calmodulin. These results indicate that Ca(2+)-calmodulin modulates the interaction of KCBP with tubulin subunits and this modulation is due to the calmodulin-binding domain in the KCBP. Calcium-dependent calmodulin modulation of KCBP interaction with tubulin suggests regulation of KCBP function by calcium, the first such regulation of a kinesin heavy chain among all the known kinesin-like proteins.
Narasimhulu
S B
SB
Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins 80523, USA.
Kao
Y L
YL
Reddy
A S
AS
D000255:Adenosine Triphosphate / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism*; D046911:Macromolecular Substances; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014404:Tubulin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D029681:Arabidopsis Proteins; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; C099551:KCBP protein, Arabidopsis; D046911:Macromolecular Substances; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014404:Tubulin; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D016547:Kinesins; D002118:Calcium