Structure of tetragonal crystals of human erythrocyte catalase.
The structure of catalase from human erythrocytes (HEC) was determined in tetragonal crystals of space group I4(1) by molecular-replacement methods, using the orthorhombic crystal structure as a search model. It was then refined in a unit cell of dimensions a = b = 203.6 and c = 144.6 A, yielding R and R(free) of 0.196 and 0.244, respectively, for all data at 2.4 A resolution. A major difference of the HEC structure in the tetragonal crystal compared with the orthorhombic structure was the omission of a 20-residue N-terminal segment corresponding to the first exon of the human catalase gene. The overall structures were otherwise identical in both crystal forms. The NADPH-binding sites were empty in all four subunits and bound water molecules were observed at the active sites. The structure of the C-terminal segment, which corresponds to the last exon, remained undetermined. The tetragonal crystals showed a pseudo-4(1)22 symmetry in molecular packing. Two similar types of lattice contact interfaces between the HEC tetramers were observed; they were related by the pseudo-dyad axes.
Safo
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MK
Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, VA 23219, USA.
Musayev
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FN
Wu
S H
SH
Abraham
D J
DJ
Ko
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TP
D002374:Catalase / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004912:Erythrocytes / Q000201:enzymology*; D005583:Fourier Analysis; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation
D002374:Catalase