The amino acid sequence LLVRGRTLVV, which is probably located in a strand-turn-strand structure, has been identified as a protein destruction signal in the rapidly degraded encephalomyocarditis virus 3C protease. Mutations within this sequence reduced the susceptibility of the 3C protease toward ubiquitination and degradation in rabbit reticulocyte lysate. This signal is transferable, since poliovirus 3C protease, which is a poor ubiquitin-mediated proteolytic system substrate, was found to be ubiquitinated and degraded when the signal sequence was either generated at an internal location in the protein or fused to the N terminus. An evaluation of the behavior of 3C protease proteins containing mutations in the signal region indicates that considerable variability in the primary structure is tolerated, although the conservation of certain features appears to be required for signal function. Two E3 ubiquitin-protein ligases that recognize the encephalomyocarditis virus 3C protease as a substrate were also partially purified. One of these was identified as the previously described E3␣, and this was shown to require the destruction signal sequence to catalyze efficiently the ubiquitination of the 3C protease. The other is a Ubc5-dependent E3 that appears to recognize a different, unidentified feature of the 3C protease.

We demonstrate here that a specific monoclonal antibody can be utilized as a physiological tool to analyze neuropeptide function. Two cardioacceleratory peptides (CAPs) have been recently isolated from the CNS of the tobacco hawkmoth, Manduca sexta (Tublitz and Truman, 1985a), and it has been suggested that they act as cardioregulatory neurohormones during adult emergence and wing inflation (Tublitz and Truman, 1985b). Evidence is presented here indicating that a monoclonal antibody, 6C5, selectively and specifically precipitated the biological activities of both CAPs. In vivo injections of 6C5 markedly reduced CAP hemolymph titers in newly emerged adults. The 6C5 treatment also blocked the primary physiological effect of the CAPs, the increase in cardiac activity seen during adult wing expansion. In addition, removal of the postemergence CAP pulse with 6C5 prolonged the duration of wing-inflation behavior. Thus, by neutralizing CAP hemolymph activity with a CAP-specific antibody, we have shown that the CAPs are involved in cardioregulation in newly emerged moths.

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The compression produced by and the resistance to pullout of the 6.5 mm cannulated Herbert screw were compared with those of ASIF headed screws. The latter were tested with and without washers and in the following sizes: 4.5 mm cortical, 6.5 mm cancellous with a 16 mm threaded segment, and 6.5 mm cancellous with a 32 mm threaded segment. Polyurethane foam was used as a substitute for cancellous bone and ASIF artificial bone for corticocancellous bone. The compression produced by a cancellous lag screw with a washer was significantly greater than that produced by a Herbert screw of equivalent size (p < 0.05). When the screws were tested using the corticocancellous composite the ASIF cancellous screw without a washer produced significantly greater compression (p < 0.05); when used with a washer the difference was highly significant (p < 0.001). The dual pitch Herbert screw is not appropriate for the management of fractures in which compression is of greater importance than the need to avoid prominence of the screw head.

No abstract