Variant subunit specificity
in the quaternary structure of Artemia hemoglobin
C.J. Vandenberg, C.M. Matthews, C.N.A. Trotman-2002
Molecular Biology and Evolution, 19(8): 1288-1291
(from Current Contents)
Abstract :
The brine shrimp Artemia has three extracellular
hemoglobins (Hbs) that are developmentally expressed and exhibit distinct
oxygen-binding characteristics (Heip, Moens, and Kondo 1978; Heip et al.
1978). These Hbs are composed of two polymers, each of which comprises nine
covalently linked globin domains. Although the cDNA sequences of two
nine-domain globins from Artemia have been published, there is evidence for
the existence of further expressed globin genes (Manning, Trotman, and Tate
1990). In the present study extensive analysis at the cDNA and genomic
levels was performed in order to determine the globin gene copy number in
Artemia. Sequence and Southern analysis suggest that four Hb polymers (T1,
T2, C1, and C2) are expressed in Artemia. In addition, there is also at
least one globin pseudogene. Protein sequencing of the native Hbs revealed
that there are limitations on which two polymers can associate. The
composition of the Hbs has been determined to be: Hb I, C1C2; Hb II, C1T2;
and Hb III, T1T2. These pairings allow the levels of the three Artemia Hbs
to be regulated independently by polymer expression alone, therefore
explaining the previously inconsistent developmental and hypoxia-induced
expression patterns.
(Univ Otago; Dept Biochem; Box 56; Dunedin; New
Zealand, e-mail of C.N.A. Trotman: clive.trotman@stonebow.otago.ac.nz)