A mitochondrial heat shock protein from Crithidia fasciculata.

MCP72 is a mitochondrial hsp70 protein from the trypanosomatid Crithidia fasciculata. An MCP72 cDNA clone was isolated from a C. fasciculata cDNA library by screening with antiserum specific for the homologous protein of Trypanosoma cruzi [9]. The MCP72 cDNA encodes a polypeptide of 663 amino acids which is 84% identical to the Trypanosoma cruzi protein and 56% identical to the Escherichia coli hsp70 protein DnaK. MCP72 is less similar to other hsp70 proteins. Native MCP72 was purified to homogeneity by ATP-agarose affinity chromatography. Comparison of its N-terminal amino acid sequence with that deduced from the cDNA sequence shows that 20 amino acid residues had been cleaved from the N-terminus; this sequence probably represents a mitochondrial import signal which is cleaved during translocation into the mitochondrion. Fluorescence microscopy, using antibodies specific for MCP72, indicates that the protein is concentrated in a region of the mitochondrial matrix which surrounds the kinetoplast.

The triad of Streptococcus bovis bacteremia, colonic pathology, and liver disease.

The association of Streptococcus bovis endocarditis and colon carcinoma has been reported previously in small series in the medical, but not surgical, literature. Although the fecal carriage rate of S. bovis increases with colonic pathology, no explanation exists for the development of bacteremia in these cases. To explore the possible contribution of hepatic dysfunction to the development of portal and systemic bacteremia, the incidence of both colonic pathology and liver disease or dysfunction was determined in 92 patients with S. bovis endocarditis and/or bacteremia. Colonic and liver evaluation had been undertaken in 47% and 93% of patients, respectively. Among these patients, colonic pathology was identified in 51%, and liver disease or dysfunction was documented in 56%. Either the underlying colonic disease or alterations in hepatic secretion of bile salts or immunoglobulins may promote the overgrowth of S. bovis and its translocation from the intestinal lumen into the portal venous system. A compromised hepatic reticuloendothelial system may then contribute to the development of S. bovis septicemia and subsequent endocarditis. We conclude that S. bovis bacteremia is an indication to the clinician of the possibility of underlying liver disease as well as colon pathology.

Physical characterization of a kinetoplast DNA fragment with unusual properties.

A 414-base pair fragment from a Leishmania tarentolae kinetoplast DNA minicircle has unusual physical properties. We reported previously that in comparison to phi X174 and pBR322 control fragments, the kinetoplast fragment behaves in gel electrophoresis, gel filtration, and electric dichroism experiments as if it has an unusually compact conformation. We accounted for these unusual properties by proposing that the fragment is a systematically bent helix (Marini, J.C., Levene, S.D., Crothers, D.M., and Englund, P.T. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7664-7668). In this paper, we further explore the properties of the kinetoplast fragment. Because of its compact conformation, the kinetoplast fragment has difficulty in snaking through polyacrylamide gels and therefore migrates unusually slowly in electrophoresis experiments. Warming (53 degrees C) and ethanol (5-20%) partially normalize gel migration; glyoxal treatment results in denatured strands with electrophoretic mobility close to that expected for their size. In vivo modification does not appear to be responsible for the fragment's properties; its anomalous electrophoretic behavior persists after proteinase K treatment, phenol extraction, or after cloning into pBR322 and reisolation. Velocity sedimentation experiments rule out fragment aggregation. Secondary structure, such as a cruciform, is not detectable by S1 or mung bean nuclease digestion. The kinetoplast fragment has circular dichroism spectra characteristic of a B-type helix. With increasing temperature, there is an increase in the 270/280 ellipticity ratio. Circular dichroism spectra taken in the presence of ethanol show a B to A helix transition at unusually low ethanol concentrations (between 44 and 54% (w/w]. Thermal denaturation reveals a triphasic melting curve.