Motor nerve palsy is uncommon following primary total hip arthroplasty. A preoperative diagnosis of developmental dysplasia of the hip or posttraumatic arthritis, the use of a posterior approach, lengthening of the extremity, and use of an uncemented femoral implant increased the odds ratio of sustaining a motor nerve palsy. The majority of the motor nerve deficits in our series, whether complete or incomplete, did not fully resolve.

SummaryDegradation of ssrA-tagged proteins is a central feature of protein-quality control in all bacteria. In Escherichia coli , the ATP-dependent ClpXP and ClpAP proteases are thought to participate in this process, but their relative contributions to degradation of ssrA-tagged proteins in vivo have been uncertain because two adaptor proteins, ClpS and SspB, can modulate proteolysis of these substrates. Here, intracellular levels of these protease components and adaptors were determined during exponential growth and as cells entered early stationary phase. Levels of ClpA and ClpP increased about threefold during this transition, whereas ClpX, ClpS and SspB levels remained nearly constant. Using GFP-ssrA expressed from the chromosome as a degradation reporter, the effects of altered concentrations of different protease components or adaptor proteins were explored. Both ClpXP and ClpAP degraded GFP-ssrA in the cell, demonstrating that wild-type levels of SspB and ClpS do not inhibit ClpAP completely. Upon entry into stationary phase, increased levels of ClpAP resulted in increased degradation of ssrA-tagged substrates. As measured by maximum turnover rates, ClpXP degradation of GFP-ssrA in vivo was significantly more efficient than in vitro . Surprisingly, ClpX-dependent ClpP-independent degradation of GFP-ssrA was also observed. Thus, unfolding of this substrate by ClpX appears to enhance intracellular degradation by other proteases.

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Conventional kinesin is a highly processive, plus-enddirected microtubule-based motor that drives membranous organelles toward the synapse in neurons. Although recent structural, biochemical, and mechanical measurements are beginning to converge into a common view of how kinesin converts the energy from ATP turnover into motion, it remains difficult to dissect experimentally the intermolecular domain cooperativity required for kinesin processivity. We report here our presteady-state kinetic analysis of a kinesin switch I mutant at Arg 210 (NXXSSRSH, residues 205-212 in Drosophila kinesin). The results show that the R210A substitution results in a dimeric kinesin that is defective for ATP hydrolysis and a motor that cannot detach from the microtubule although ATP binding and microtubule association occur. We propose a mechanistic model in which ATP binding at head 1 leads to the plus-end-directed motion of the neck linker to position head 2 forward at the next microtubule binding site. However, ATP hydrolysis is required at head 1 to lock head 2 onto the microtubule in a tight binding state before head 1 dissociation from the microtubule. This mechanism optimizes forward movement and processivity by ensuring that one motor domain is tightly bound to the microtubule before the second can detach.Kinesin is a highly processive, dimeric mechanoenzyme that travels along microtubules toward their plus-ends in discrete 8-nm steps, each step tightly coupled to a single ATP turnover (1-3). Recent evidence from a variety of experimental approaches has focused our attention to the proposal presented by Rice et al. (4) that ATP binding induces a pronounced conformational change in the neck linker region, which docks the neck linker onto the catalytic core and propels the unattached kinesin head forward to find the next binding site on the microtubule. This model is based on a disorder-to-order transition in the neck linker region for monomeric kinesin constructs. The neck linker of the Mt⅐K 1 complex was shown to be mobile in the presence of ADP, existing in an equilibrium with two predominant conformations trapped by cryo-electron microscopy. However, upon the addition of ATP or nonhydrolyzable ATP analogs to the Mt⅐K complex, the neck mobility ceased with the neck linker element tightly associated with the catalytic core. This ordered state was reversed by the addition of ADP or loss of nucleotide. In addition, the cryo-electron microscopy of this proposed ATP state revealed a single discrete orientation of the neck linker with the carboxyl terminus of the motor domain directed toward the plus-end of the microtubule (4). Xing et al. (5) have reported for a monomeric kinesin motor domain two discrete structural transitions induced by ADP binding and another produced by ATP binding. These three conformations revealed by fluorescence resonance energy transfer were consistent with the results reported by Rice et al. (4). Furthermore, biochemical studies of dimeric kinesin have demonstrated that ATP binding (or nonhydrolyzabl...

A patient-derived questionnaire can provide a high level of agreement with surgeon assessments of outcome following shoulder surgery. Patient-administered methods should continue to be evaluated as a means of assessment of these patients.