COORDINATE SYNTHESIS AND TURNOVER OF HEAT-SHOCK PROTEINS IN BORRELIA-BURGDORFERI - DEGRADATION OF DNAK DURING RECOVERY FROM HEAT-SHOCK

The synthesis and turnover of heat shock proteins (Hsps) by Borrelia b urgdorferi, the Lyme disease spirochete, was investigated by radiolabe ling of whole spirochetes and spheroplasts, comparison of one- and two -dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis , and use of immunochemistry, The approximate to 72-kDa DnaK homolog a nd three additional Hsps of 39, 27, and 21 kDa increased in amount by 3- to 15-fold between 2 and 6 h following temperature upshift from 28 to 39 degrees C, Temperature downshift experiments following the trans fer of spirochetes from 40 to 28 degrees C showed that within 15 to 30 min, synthesis of most of the major Hsps returned to levels seen in s pirochetes statically maintained at the lower temperature, Spheroplast s of B. burgdorferi produced by treatment with EDTA and lysozyme were radiolabeled, and specific Hsps were localized to either the cytoplasm or membrane fraction, Further analysis by two-dimensional electrophor esis demonstrated three constitutively expressed DnaK isoforms with pI s near 5.5, A pattern suggestive of DnaK degradation was observed foll owing recovery from heat shock but not in spirochetes maintained entir ely at a low temperature, Some of these putative degradation products were recognized by monoclonal antibodies directed against the B. burgd orferi DnaK protein. These data suggest that following a period of pea k synthesis, DnaK is actively degraded as the spirochete reestablishes its metabolic thermometer, These findings provide a new interpretatio n of previous work suggesting that 10 to 15 B. burgdorferi polypeptide s, including DnaK have a common epitope.