The archaeogastropod mollusc Haliotis iris : tissue and blood metabolites and allosteric regulation of haemocyanin function Jane

known by the Maori name, paua) belongs to an ancient morphologically conservative group, the Archaeogastropoda (Andrews, 1988). Blood concentrations of the oxygentransporting protein haemocyanin (Hc) show remarkably high individual variability in Haliotis species (Pilson, 1965; Ainslie, 1980a) (H. H. Taylor and J. E. Taylor, unpublished data for H. iris). Nevertheless, oxygen-binding studies suggest that the pigment plays a quantitatively important role, transporting more than 80 % of the O2 delivered to the tissues (Ainslie, 1980b). Ultrastructural, immunocytochemical and cDNA hybridisation studies strongly implicate rhogocytes (pore cells), located in connective tissues of the mantle, digestive gland and foot, as the site of Hc biosynthesis in Haliotis spp. and other gastropods (Sminia and Boer, 1973; Sminia and Vlugt van Dalen, 1977; Hazprunar, 1996; Taylor and Anstiss, 1999; Albrecht et al., 2001). As in other gastropods, the Hc of Haliotis exists primarily as a didecamer of approximately 8 MDa with a hollow cylindrical quaternary structure, comprising 20 subunits of approximately 400 kDa each, arranged as two end-to-end ring-shaped decamers. However, variable proportions of decamers and multidecamers are also present (van Holde and Miller, 1995; Söhngen et al., 1997; Harris et al., 2000). Each subunit is folded into eight functional units of approximately 50 kDa (Ellerton and Lankovsky, 1983; Ellerton et al., 1983; Keller et al., 1999), each reversibly binding one O2 molecule at a binuclear copper site (van Holde and Miller, 1995). H. tuberculata Hc exists in two isoforms (HtH1 and HtH2) (Keller et al., 1999; Lieb et al., 1999, 2000; Harris et al., 2000; Meissner et al., 2000), which correspond immunologically to the much-studied KLH1 and KLH2 isoforms of another archaeogastropod, the keyhole limpet Megathuria crenulata (Gebauer et al., 1994; Söhngen et al., 1997). Considerable progress has been made in elucidating 253 The Journal of Experimental Biology 205, 253–263 (2002) Printed in Great Britain © The Company of Biologists Limited 2002 JEB3731