Running energetics in the pronghorn antelope

The pronghorn antelope (Antilocapra americana) has an alleged top speed of 100 km h-1, second only to the cheetah (Acionyx jubatus) among land vertebrates, a possible response to predation in the exposed habitat of the North American prairie. Unlike cheetahs, however, pronghorn antelope are distance runners rather than sprinters, and can run 11 km in 10 min, an average speed of 65 km h-1. We measured maximum oxygen uptake in pronghorn antelope to distinguish between two potential explanations for this ability: either they have evolved a uniquely high muscular efficiency (low cost of transport) or they can supply oxygen to the muscles at unusually high levels. Because the cost of transport (energy per unit distance covered per unit body mass) varies as a predictable function of body mass among terrestrial vertebrates, we can calculate the predicted cost to maintain speeds of 65 and 100 km h-1 in an average 32-kg animal. The resulting range of predicted values, 3.2-5.1 ml O2 kg-1 s-1, far surpasses the predicted maximum aerobic capacity of a 32-kg mammal (1.5 ml O2 kg-1 s-1). We conclude that their performance is achieved by an extraordinary capacity to consume and process enough oxygen to support a predicted running speed greater than 20 ms-1 (70 km h-1), attained without unique respiratory-system structures.     

A coat subunit of Golgi-derived non-clathrin-coated vesicles with homology to the clathrin-coated vesicle coat protein beta-adaptin

Four high-molecular-weight proteins form the main subunits of the coat of Golgi-derived (non-clathrin) coated vesicles. One of these coat proteins, beta-COP, is identical to a Golgi-associated protein of relative mass 110,000 (110K) that shares homology with the adaptin proteins of clathrin-coated vesicles. This connection, and the comparable molecular weights of the coat proteins of Golgi-derived and clathrin-coated vesicles, indicates that they may be structurally related. The identification of beta-COP as the 110K protein explains the blocking of secretion by the drug brefeldin A.     

A homologue of the bacterial heat-shock gene DnaJ that alters protein sorting in yeast

Heat-shock proteins have been implicated in assembly of protein complexes, correct protein folding and uptake of proteins into organelles. In Escherichia coli, the heat-shock protein DnaJ and the Hsp70 homologue, DnaK, act together to disassemble a protein complex involved in bacteriophage lambda replication. We report the identification of SCJ1, a gene in the yeast Saccharomyces cerevisiae that encodes a homologue of the bacterial DnaJ protein. SCJ1 was identified by a genetic screen in which increased expression of candidate genes results in missorting of a nuclear-targeted test protein. The predicted amino-acid sequence of SCJ1 is 37% identical to the entire E. coli DnaJ protein. Hybridization experiments indicate that there is a family of yeast genes related to SCJ1. These findings suggest that the Hsp70 DnaK-DnaJ interaction is general to eukaryotes.     

New use of BCG for recombinant vaccines

BCG, a live attenuated tubercle bacillus, is the most widely used vaccine in the world and is also a useful vaccine vehicle for delivering protective antigens of multiple pathogens. Extrachromosomal and integrative expression vectors carrying the regulatory sequences for major BCG heat-shock proteins have been developed to allow expression of foreign antigens in BCG. These recombinant BCG strains can elicit long-lasting humoral and cellular immune responses to foreign antigens in mice.     

A pseudoknot-like structure required for efficient self-cleavage of hepatitis delta virus RNA

Hepatitis delta virus genomic and antigenomic RNAs contain a self-cleavage site hypothesized to function in processing the viral RNA during replication. Self-cleavage requires only a divalent cation and is mediated at the genomic site by a sequence of less than 85 nucleotides. We propose that the genomic self-cleaving sequence element and a corresponding sequence from the anti-genomic RNA could generate related secondary structures. The region of the antigenomic sequence, predicted from the proposed structure, was synthesized and shown to be sufficient for self-cleavage. Evidence for two stems which form a tertiary interaction was obtained by site-specific mutagenesis of the antigenomic sequence. Efficient self-cleavage in 10 M formamide or 5 M urea, also a property of the genomic sequence, was dependent on base-pairing in both stems. But in the absence of denaturants, the stem distal to the site of cleavage was not required, suggesting that the tertiary interaction stabilizes the structure required for self-cleavage.     

A novel cyclin encoded by a bcl1-linked candidate oncogene

We have previously identified a candidate oncogene (PRAD1 or D11S287E) on chromosome 11q13 which is clonally rearranged with the parathyroid hormone locus in a subset of benign parathyroid tumours. We now report that a cloned human placental PRAD1 complementary DNA encodes a protein of 295 amino acids with sequence similarities to the cyclins. Cyclins can form a complex with and activate p34cdc2 protein kinase, thereby regulating progress through the cell cycle. PRAD 1 messenger RNA levels vary dramatically across the cell cycle in HeLa cells. Addition of the PRAD1 protein to interphase clam embryo lysates containing inactive p34cdc2 kinase and lacking endogenous cyclins allows it to be isolated using beads bearing p13suc1, a yeast protein that binds cdc2 and related kinases with high affinity and coprecipitates kinase-associated proteins. Addition of PRAD1 also induces phosphorylation of histone H1, a preferred substrate of cdc2. These data suggest that PRAD1 encodes a novel cyclin whose overexpression may play an important part in the development of various tumours with abnormalities in 11q13.