The alkaline transition of blue copper proteins, Cucumis sativus plastocyanin and Pseudomonas aeruginosa azurin

Abstract

Autoreduction of Cucumis sativus plastocyanin and Pseudomonas aeruginosa azurin took place at alkaline pHs, having been accompanied by the decrease in the intensities of the charge transfer band, Cys-S-(π)→Cu(II) at 597 and 626 nm, and the Cu(II)-EPR signals with small AII values of 6.5 x 10-3 and 5.3 x 10-3 cm-1 for plastocyanin and azurin, respectively. Further, an extra Cu(II)-EPR signal with a large AII value of 21 x 10-3 cm-1 also reversibly emerged with increasing pH. Plastocyanin and azurin are in an equilibrium of the three forms at alkaline pHs Dear Professor Richard Cogdell Editor FEBS LettersThank you very much for your suggestion to tidy us some of English before to submit the revised manuscript to FEBS Letters (FEBSLETTERS-S-05-01041R1). English was polished up by the professional English correction service as follows.About twenty "the" and "a' were deleted or added (not indicated).About fifteen commas were added (not indicated).Every "pH's" was converted to "pHs".Single form was changed to plural form and vice versa for some points.Other alterations are as follows. P2. Line 3: "has not been known" was change to "has not been hitherto understood". P2. Line 16: "solved" was deleted.P2. Line 17: "that" which had been deleted in the original manuscript was added.P2. Line 23 and others: "high alkaline pH's" was changed to "highly alkaline pHs". P3. Line 3: "till" was changed to "until".P3. Results and discussion, Lines 7 and 11 The order of words were changed from "slightly shifted" to "shifted slightly" and "in only" to "only in".P3. Line 5 from bottom: "with the spin Hamiltonian parameters" was added after "signal" and "typical to" was changed to "typical of". P4. Line 6: "recovered as that" was changed to "recovered to the level of that". P4. Line 11: "not only Pc was reduced" was changed to "not only was Pc reduced,". P4. Line 17: "the form to give" was changed to "the form giving". P4. Line 18: "In order to ascertain that" was converted to "In order to ascertain whether". P5. Line 21: "As conclusion" was changed to "In conclusion". P5. Line 3 from bottom: "under study" was changed to "being studied as to".Titles of cited papers were checked to be correct. Sincerely yours, Takeshi Sakurai Cover LetterAbout twenty "the" and "a' were deleted or added (not indicated).About fifteen commas were added (not indicated).Every "pH's" was converted to "pHs".Single form was changed to plural form and vice versa for some points.Other alterations are as follows. P2. Line 3: "has not been known" was change to "has not been hitherto understood". P2. Line 16: "solved" was deleted.P2. Line 17: "that" which had been deleted in the original manuscript was added.P2. Line 23 and others: "high alkaline pH's" was changed to "highly alkaline pHs". P3. Line 3: "till" was changed to "until".P3. Results and discussion, Lines 7 and 11 The order of words were changed from "slightly shifted" to "shifted slightly" and "in only" to "only in".P3. Line 5 from bottom: "with the spin Hamiltonian parameters" was added after "s...

Basic and applied features of multicopper oxidases, CueO, bilirubin oxidase, and laccase

“…However, the expressed MCOs as isolated, which have not experienced reaction, sometimes show an extra Cu EPR signal with the | A z| value, ∼10 × 10 −3 cm −1 , possibly originated in an uncoupled type III Cu in a mixed valence state, although turnover of the reaction gave the spectra due to the resting form of the MCO 27. In accordance with this, possible delocalization of a radical on type I Cu and the S atom of the Cys residue depending on pH was observed28 as has also been observed for blue Cu proteins 29. Changes in the EPR spectral features depending on pH and temperature are due to deprotonation from the coordinated H 2 O to type II Cu and conformational change of the protein molecules, respectively.…”

Experimental evidence for a link among cupredoxins: Red, blue, and purple copper transformations in nitrous oxide reductase

“…Native holo N 2 OR has also been widely investigated, and its various copper chromophores (both Cu A and Cu Z ) and their spectroscopic properties have been reported as well as Cu A reconstitution by using Cu(II)(en) 2 SO 4 (49-51). pH titrations of preformed Cu A sites, as well as T1 sites, also results in a perturbation of the copper active site (41,(52)(53)(54)(55)(56). Originally, copper sites were classified as T1, T2, or T3, but the classification scheme was modified with the discovery of Cu A .…”

Structure and function of type I copper in multicopper oxidases

“…Blue copper proteins show a so-called "alkaline transition" of their absorption wavelength, absorption intensity, and redox potential [91][92][93][94]. With increasing pH, especially at pH 8-11, the absorption maximum at ca.…”

“…With increasing pH values higher than 7, the characteristic blue color faded reversibly and the intensity of the type I copper EPR signal also changed concomitantly with the absorption change. "Autoreduction" is supposed to be derived from a shift in the equilibrium between Cu 2+ -S -and Cu + -S • depending on the pH [94]. When the radical center is delocalized on the sulfur atom, copper is formally in the cuprous state and S • may not give an EPR signal because of broadening.…”