TY - JOUR
T1 - X-ray structure of β-carbonic anhydrase from the red alga, Porphyridium purpureum, reveals a novel catalytic site for CO2 hydration
AU - Mitsuhashi, Satoshi
AU - Mizushima, Tsunehiro
AU - Yamashita, Eiki
AU - Yamamoto, Masaki
AU - Kumasaka, Takashi
AU - Moriyama, Hideaki
AU - Ueki, Tatzuo
AU - Miyachi, Shigetoh
AU - Tsukihara, Tomitake
PY - 2000/2/25
Y1 - 2000/2/25
N2 - The carbonic anhydrases (CAs) fall into three evolutionarily distinct families designated α-, β-, and γ-CAs based on their primary structure. β-CAs are present in higher plants, algae, and prokaryotes, and are involved in inorganic carbon utilization. Here, we describe the novel x-ray structure of β-CA from the red alga, Porphyridium purpureum, at 2.2-Å resolution using intrinsic zinc multiwavelength anomalous diffraction phasing. The CA monomer is composed of two internally repeating structures, being folded as a pair of fundamentally equivalent motifs of an α/β domain and three projecting α-helices. The motif is obviously distinct from that of either α- or γ-CAs. This homodimeric CA appears like a tetramer with a pseudo 222 symmetry. The active site zinc is coordinated by a Cys-Asp-His-Cys tetrad that is strictly conserved among the β-CAs. No water molecule is found in a zinc-liganding radius, indicating that the zinc-hydroxide mechanism in α- CAs, and possibly in γ-CAs, is not directly applicable to the case in β- CAs. Zinc coordination environments of the CAs provide an interesting example of the convergent evolution of distinct catalytic sites required for the same CO2 hydration reaction.
AB - The carbonic anhydrases (CAs) fall into three evolutionarily distinct families designated α-, β-, and γ-CAs based on their primary structure. β-CAs are present in higher plants, algae, and prokaryotes, and are involved in inorganic carbon utilization. Here, we describe the novel x-ray structure of β-CA from the red alga, Porphyridium purpureum, at 2.2-Å resolution using intrinsic zinc multiwavelength anomalous diffraction phasing. The CA monomer is composed of two internally repeating structures, being folded as a pair of fundamentally equivalent motifs of an α/β domain and three projecting α-helices. The motif is obviously distinct from that of either α- or γ-CAs. This homodimeric CA appears like a tetramer with a pseudo 222 symmetry. The active site zinc is coordinated by a Cys-Asp-His-Cys tetrad that is strictly conserved among the β-CAs. No water molecule is found in a zinc-liganding radius, indicating that the zinc-hydroxide mechanism in α- CAs, and possibly in γ-CAs, is not directly applicable to the case in β- CAs. Zinc coordination environments of the CAs provide an interesting example of the convergent evolution of distinct catalytic sites required for the same CO2 hydration reaction.
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U2 - 10.1074/jbc.275.8.5521
DO - 10.1074/jbc.275.8.5521
M3 - Article
C2 - 10681531
AN - SCOPUS:0034050126
VL - 275
SP - 5521
EP - 5526
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 8
ER -