Kinesin tail domains and Mg2+ directly inhibit release of ADP from head domains in the absence of microtubules.

Kinesin-1 is a vesicle motor that can fold into a compact inhibited conformation that is produced by interaction of the heavy chain C-terminal tail region with the N-terminal motor domains (heads). Binding of the tail domains to the heads inhibits net microtubule-stimulated ATPase activity by blocking the ability of the heads to bind to microtubules with coupled acceleration of ADP release. We now show that folding of kinesin-1 also directly inhibits ADP release even in the absence of microtubules.

Modulation of kinesin half-site ADP release and kinetic processivity by a spacer between the head groups.

A series of modifications of the junction of the neck linker and neck coil of dimeric Drosophila kinesin were constructed to determine the influence of head orientation and spacing on the ATPase kinetics. Ala(345) is the first residue in the coiled-coil of the neck, and its replacement with glycine or proline produces no significant change in the k(cat) or K(0.5(MT)) values for activation of their ATPase by microtubules (MTs) or in their k(bi(ratio)) value for the average number of ATP molecules hydrolyzed during a processive encounter with a MT.

The kinesin family member BimC contains a second microtubule binding region attached to the N terminus of the motor domain.

The kinesin family member BimC has a highly positively charged domain of approximately 70 amino acids at the N terminus of the motor domain. Motor domain constructs of BimC were prepared with and without this extra domain to determine its influence. The level of microtubules needed for half saturation of the ATPase of BimC motor domain constructs is reduced by approximately 7000-fold at low ionic strength upon addition of this extra N-terminal extension.

The Development of a Standard Reference Material for Calibration of the University of Pittsburgh Smoke Toxicity Method for Assessing the Acute Inhalation Toxicity of Combustion Products.

A standard reference material (SRM 1049) has been developed for the University of Pittsburgh smoke toxicity method. SRM 1049 is a nylon 6/6 and has the molecular structure of [-NH(CH)NHCO(CH)CO-] . This SRM is for calibrating the apparatus and providing confidence that the method is being conducted in a correct manner and that the equipment is functioning properly.