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The terrestric oligochaete worm Enchytraeus buchholzi survives in cadmium (Cd)-polluted environments by aid of its Cd-inducible 25 kDa cysteine-rich protein (CRP). Here, we analyze promoter and structure of the crp gene and compare its relationship to MT genes. The crp gene, approximately 12 kbp long, consists of 10 exons with exons 2 to 9 encoding eight almost identical repeats of predominantly 31 amino acids of the CRP. The introns of the crp gene contain various repetitive elements including retrotransposon-like sequences. The 683-bp promoter of the non-constitutive crp gene exhibits a much higher basal activity than the mouse MT-II promoter in HepG2 cells. Essential for crp promoter activity is the distal region (-683/-521) with a GC box and the proximal region (-308/-8) with the four MREa, b, c, d and AP-1, -2, -3 elements, whereas the central portion (-521/-309) with CAAT box, CRE and a XRE causes promoter repression. The TATA box-, MREc- and the AP-2, -3-containing region are required for high crp promoter activity. Our data support the view that the crp gene is a unique MT-gene and has evolved by exon duplications from a MT-like ancestral gene.

The nematode Haemonchus contortus is an important parasite of cattle and sheep. We describe here the cloning of a cDNA encoding a 53 kDa hexokinase (EC 2.7.1.1). The deduced protein shows 73% identity to a 50 kDa hexokinase deduced from a Caenorhabditis elegans cosmid. Alignment with mammalian hexokinases reveals two short amino acid insertions in the H. contortus hexokinase. Software tools for structural protein analysis (ExPASy server, Geneva) localize these insertions on the surface of the molecule, suggesting these surface changes as potential target sites for chemotherapeutic drugs.