Intracellular proteolytic activity in developing myxospores of Myxococcus xanthus |
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Authors: | Michael Orlowski David White |
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Affiliation: | 1. Department of Microbiology, Indiana University, 47401, Bloomington, Indiana
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Abstract: | - Cell-free extracts from vegetative cells and developing myxospores of Myxococcus xanthus were found to contain similar amounts of proteolytic activity, approximately 80% of which was due to one or more neutral metal proteases.
- Sixty per cent of the proteolytic activity was particulate.
- The specific activity of the proteases was high throughout all stages of myxospore formation and displayed small increases in activity at two stages of development: (1) during cell shortening and (2) immediately following the conversion to spheres. The first peak in activity was apparent in assays conducted at pH 8 or 10 whereas the second peak was obvious only at pH 6.
- A mutant which develops into myxospores only after a lag of approximately 7–8 h possessed levels of proteases similar to the wild type and displayed a peak in proteolytic activity after a delay of 7–8 h.
- Low levels of serine protease activity were occasionally detected in both vegetative cells and myxospores; no sulfhydryl proteases were detectable in either cell type.
- Extracellular proteases accumulated in the medium throughout myxospore development but differed from the intracellular proteases in pH optima and sensitivity to inhibitors.
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