title: Tryptophan phosphorescence of the Ca2+-ATPase of sarcoplasmic reticulum.
abstract: Phosphorescence of protein tryptophan was analyzed in sarcoplasmic reticulum vesicles, and in the purified Ca2+ transport ATPase in deoxygenated aqueous solutions at room temperature. Upon excitation with light of 295 nm wavelength, the emission maxima of fluorescence and phosphorescence were at 330 nm and at 445 nm, respectively. The phosphorescence decay was multiexponential; the lifetime of the long-lived component of phosphorescence was approximately equal to 22 ms. ATP and vandate significantly reduced the phosphorescence in the presence of either Ca2+ or EGTA; ADP was less effective, while AMP was without effect. The quenching by ATP showed saturation consistent with the idea that the ATP-enzyme complex had a lower phosphorescence yield. Upon exhaustion of ATP, the phosphorescence returned to starting level. Significant quenching of phosphorescence with a decrease in phosphorescence lifetime was also caused by NaNO2, methylvinyl ketone and trichloroacetate, without effect on ATPase activity; this quenching did not show saturation and was therefore probably collisional in nature.
authors.affiliation: Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104.
authors.forename: J M
authors.initials: JM
authors.lastname: Vanderkooi
authors.forename: S
authors.initials: S
authors.lastname: Papp
authors.forename: S
authors.initials: S
authors.lastname: Pikula
authors.forename: A
authors.initials: A
authors.lastname: Martonosi
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002074:Butanones / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008163:Luminescent Measurements; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D012977:Sodium Nitrite / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D014238:Trichloroacetic Acid / Q000494:pharmacology; D014364:Tryptophan; D014638:Vanadates / Q000494:pharmacology
chemical_list: D002074:Butanones; D014638:Vanadates; D004533:Egtazic Acid; D014238:Trichloroacetic Acid; D014364:Tryptophan; D000255:Adenosine Triphosphate; C057920:3-buten-2-one; D000252:Calcium-Transporting ATPases; D012977:Sodium Nitrite; D002118:Calcium