Abstract
The heat-shock response of Euglena gracilis was studied by pulse-labeling cells with [35S]sulfate at both the normal growth temperature (21°C) and an elevated temperature (36°C). Analysis of the labeled proteins by polyacrylamide gel electrophoresis indicated that the rate of synthesis of at least 3 major and 15 minor polypeptides increased in cells grown at the higher temperature. Three of the proteins appear to be immunologically related to the ubiquitous ≈70-kDa heat-shock protein (Hsp70) family. One protein of 68 kDa was found in the cytoplasm (P68cyt) and was the major heat-shock protein in Euglena gracilis. Two other proteins, 68 and 70 kDa, were localized in mitochondria (P68mit) and chloroplasts (P70chl), respectively, and they crossreacted with a polyclonal antibody raised against the Escherichia coli heat-shock protein DnaK. Like DnaK, P68mit and P70chl could be phosphorylated in vitro with [γ-32P]ATP in a reaction that was stimulated by Ca2+. A protein with characteristics similar to those of P70chl was also found in chloroplasts isolated from maize and spinach.
Original language | American English |
---|---|
Pages (from-to) | 1749-1752 |
Number of pages | 4 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 87 |
Issue number | 5 |
State | Published - Mar 1990 |
Externally published | Yes |
ASJC Scopus subject areas
- General
Keywords
- Heat-shock proteins
- Organelles
- Phosphorylation