Crystal structures, spectroscopic features, and catalytic properties of cobalt(II), copper(II), nickel(II), and mercury(II) derivatives of the zinc endopeptidase astacin. A correlation of structure and proteolytic activity.
The catalytic zinc ion of astacin, a prototypical metalloproteinase from crayfish, has been substituted by Co(II), Cu(II), Hg(II), and Ni(II) in order to probe the role of the metal for both catalysis and structure. Compared to Zn(II)-astacin, Co(II)- and Cu(II)-astacin display enzymatic activities of about 140 and 37%, respectively, while Ni(II)- and Hg(II)-astacin are almost inactive. The electron paramagnetic resonance spectrum of Cu(II)-astacin is typical of 5-fold coordinated copper(II), and its intense absorption maxima at 445 and 325 nm are probably due to ligand-metal charge-transfer transitions involving Tyr-149. This residue had been identified previously by x-ray crystallography of the zinc enzyme as a zinc ligand, in addition to three imidazoles and a glutamic acid-bound water molecule. We present now the refined high-resolution x-ray crystal structures of Cu(II)-, Co(II)-, and Ni(II)-astacin, which exhibit a virtually identical protein framework to the previously analyzed structures of Zn(II)-, apo-, and Hg(II)-astacin. In Co(II)- and Cu(II)-astacin, the metal is penta-coordinated similarly to the native zinc enzyme. In the Ni(II) derivative, however, an additional solvent molecule expands the metal coordination sphere to a distorted octahedral ligand geometry, while in Hg(II)-astacin, no ordered solvent molecule at all is observed in the inner coordination sphere of the metal. This indicates a close correlation between catalytic properties and ground-state metal coordination of astacin.
Gomis-Rüth
F X
FX
Max-Planck-Institut für Biochemie, Martinsried, Germany.
Grams
F
F
Yiallouros
I
I
Nar
H
H
Küsthardt
U
U
Zwilling
R
R
Bode
W
W
Stöcker
W
W
D000595:Amino Acid Sequence; D000818:Animals; D003400:Astacoidea; D001665:Binding Sites; D002413:Cations, Divalent; D003035:Cobalt; D003300:Copper; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008628:Mercury; D008666:Metalloendopeptidases / Q000737:chemistry / Q000648:ultrastructure*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009532:Nickel; D017434:Protein Structure, Tertiary; D013057:Spectrum Analysis; D015032:Zinc
D002413:Cations, Divalent; D003035:Cobalt; D003300:Copper; D009532:Nickel; D008666:Metalloendopeptidases; C071288:astacin; D008628:Mercury; D015032:Zinc