Abstract
We have already described that photo-oxidation of the sarcoplasmic reticulum Ca 2+-ATPase with the halogenated dye erythrosin B produces inhibition of the ATPase activity (J.A. Mignaco et al., Biochemistry 35 (1996) 3886–3891). We now show that the Ca 2+-dependent and Ca 2+-independent p-nitrophenylphosphatase activities are also inhibited by this treatment. Modification of rapidly (<10 min) oxidized residue(s) is responsible for the major loss of ATPase activity, whereas photo-inhibition of the phosphatase activities occurs more slowly ( t 1/2 20–30 min). Here we have focused on photo-inhibition of the Ca 2+-independent pNPPase activity, and the counteracting effects of ATP and FITC. Following photo-oxidation, the Ca 2+-independent pNPPase activity decreases monotonically. ATP partially protects against the inactivation of the pNPPase, whereas labeling the enzyme with FITC does not. However, the protective effect of ATP is completely abolished by the attached FITC. These data are interpreted in terms of two different sites that are susceptible to photo-oxidation and are involved in different events related to substrate hydrolysis.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
