Does 13C-or 15N-labeling affect Cu(I)-thiolate cluster arrangement in yeast copper-metallothionein?
It was attempted to examine whether or not isotope labeling may possibly affect an oligonuclear metal-thiolate cluster. Cu-metallothioneins are known to contain strongly distorted Cu-thiolate clusters and seemed appropriate for this study. Thus, yeast 13C-and 15N-Cu-metallothioneins were isolated from Saccharomyces cerevisiae cells grown in a minimal synthetic medium and some physicochemical parameters were compared with those of the unlabeled Cu-thionein. Surprisingly, the 13C- and 15N- labeled Cu7-thioneins are distinctly different in their characteristic spectroscopic properties. The electronic absorption was blue-shifted while both luminescence emission and chiroptic features display a distinct red shift with markedly diminished intensities, respectively. Contrary to common knowledge that isotope labeling does not affect the molecular architecture of a protein the present results support such a phenomenon. Attributable to the fortunate happenstance that there is a strongly distorted structural situation in the oligonuclear Cu-thiolate cluster this isotope effect came to light.
Hartmann
Hans-Jürgen
HJ
Anorganische Biochemie, Physiologisch-chemisches Institut der Eberhard-Karls-Universität Tübingen, Hoppe-Seyler Str. 4, 72072 Tübingen, Germany.
Kaup
Yoka
Y
Weser
Ulrich
U
D002247:Carbon Isotopes; D002352:Carrier Proteins; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism*; D007554:Isotopes / Q000737:chemistry / Q000378:metabolism*; D008163:Luminescent Measurements; D008668:Metallothionein / Q000302:isolation & purification / Q000378:metabolism*; D009587:Nitrogen Isotopes; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013053:Spectrophotometry; D013054:Spectrophotometry, Atomic
C500769:CUP1-1 protein, S cerevisiae; D002247:Carbon Isotopes; D002352:Carrier Proteins; D007554:Isotopes; D009587:Nitrogen Isotopes; C007121:copper thionein; D003300:Copper; D008668:Metallothionein