[Characteristics of δ-Aminolevulinic Acid Dehydratase of the Cold-Water Sponge Halisarca dujardinii].

δ-Aminolevulinic acid dehydratase (ALAD) is a key enzyme of the cytoplasmic heme biosynthesis pathway. The primary structure of the ALAD gene, the multimeric structure of the ALAD/hemB protein, and ALAD expression during the annual reproductive cycle were studied in the cold-water marine sponge Halisarca dujardinii. The results implicated the GATA-1 transcription factor and DNA methylation in regulating ALAD expression. Re-aggregation of sponge cells was accompanied by a decrease in ALAD expression and a change in the cell content of an active ALAD/hemB form. Further study of heme biosynthesis and the role of ALAD/hemB in morphogenesis of basal animals may provide new opportunities for treating pathologies in higher animals.

[Structure of Neuroglobin from Cold-Water Sponge Halisarca dujardinii].

The iron-containing protein neuroglobin (Ngb) involved in the transport of oxygen is generally considered the precursor of all animal globins. In this report, we studied the structure of Ngb of the cold-water sponge Halisarca dujardinii. In sponges, the oldest multicellular organisms, the Ngb gene contains three introns. In contrast to human Ngb, its promoter contains a TATA-box, rather than CG-rich motifs. In sponges, Ngb consists of 169 amino acids showing rather low similarity with its mammalian orthologues. It lacks Glu and Arg residues in positions required for prevention of hypoxia-related apoptosis. Nevertheless, Ngb contains both proximal and distal conserved heme-biding histidines. The primary structure of H. dujardinii neuroglobin predicted by sequencing was confirmed by mass-spectrometry analysis of recombinant Ngb expressed in E. coli. The high level of Ngb expression in sponge tissues suggests its possible involvement in the gas metabolism and presumably in other key metabolic processes in H. dujardinii.