A kinesin mutation that uncouples motor domains and desensitizes the gamma-phosphate sensor.
Conventional kinesin is a processive, microtubule-based motor protein that drives movements of membranous organelles in neurons. Amino acid Thr(291) of Drosophila kinesin heavy chain is identical in all superfamily members and is located in alpha-helix 5 on the microtubule-binding surface of the catalytic motor domain. Substitution of methionine at Thr(291) results in complete loss of function in vivo. In vitro, the T291M mutation disrupts the ATPase cross-bridge cycle of a kinesin motor/neck construct, K401-4 (Brendza, K. M., Rose, D. J., Gilbert, S. P., and Saxton, W. M. (1999) J. Biol. Chem. 274, 31506-31514). The pre-steady-state kinetic analysis presented here shows that ATP binding is weakened significantly, and the rate of ATP hydrolysis is increased. The mutant motor also fails to distinguish ATP from ADP, suggesting that the contacts important for sensing the gamma-phosphate have been altered. The results indicate that there is a signaling defect between the motor domains of the T291M dimer. The ATPase cycles of the two motor domains appear to become kinetically uncoupled, causing them to work more independently rather than in the strict, coordinated fashion that is typical of kinesin.
Brendza
K M
KM
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Sontag
C A
CA
Saxton
W M
WM
Gilbert
S P
SP
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics; D000255:Adenosine Triphosphate / Q000737:chemistry*; D000818:Animals; D006868:Hydrolysis; D016547:Kinesins / Q000737:chemistry* / Q000235:genetics; D007700:Kinetics; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics; D009154:Mutation; D011487:Protein Conformation
D020409:Molecular Motor Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D016547:Kinesins