The Structure of a Functional Unit from the Wall of a Gastropod Hemocyanin Offers a Possible Mechanism for Cooperativity

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• 作者：Markus Perbandt ; Eckhart W. Guth&ouml ; hrlein ; Wojciech Rypniewski ; Krassimira Idakieva ; Stanka Stoeva ; Wolfgang Voelter ; Nicolay Genov ; and Christian Betzel
• 刊名：Biochemistry
• 出版年：2003
• 出版时间：June 3, 2003
• 年：2003
• 卷：42
• 期：21
• 页码：6341 - 6346
• 全文大小：386K
• 年卷期：v.42,no.21(June 3, 2003)
• ISSN：1520-4995

文摘

Structure-function relationships in a molluscan hemocyanin have been investigated bydetermining the crystal structure of the Rapana thomasiana (gastropod) hemocyanin functional unit RtH2ein deoxygenated form at 3.38 Å resolution. This is the first X-ray structure of an unit from the wall of themolluscan hemocyanin cylinder. The crystal structure of RtH2e demonstrates molecular self-assembly ofsix identical molecules forming a regular hexameric cylinder. This suggests how the functional units areordered in the wall of the native molluscan hemocyanins. The molecular arrangement is stabilized byspecific protomer-to-protomer interactions, which are probably typical for the functional units buildingthe wall of the cylinders. A molecular mechanism for cooperative dioxygen binding in molluscanhemocyanins is proposed on the basis of the molecular interactions between the protomers. In particular,the deoxygenated RtH2e structure reveals a tunnel leading from two opposite sides of the molecule to theactive site. The tunnel represents a possible entrance pathway for dioxygen molecules. No such tunnelshave been observed in the crystal structure of the oxy-Odg, a functional unit from the Octopus dofleini(cephalopod) hemocyanin in oxygenated form.