engleski

Nm23-SD1 protein from marine sponge Suberites domuncula

Nucleoside diphosphate kinases Nm23/NDPK are enzymes that are conserved throughout evolution and are present in all tree domains of life: Bacteria, Archaea and Eukarya. The human nm23-H1/NDPK was recognized as a first metastasis suppressor gene and is the most studied member of Nm23/NDPK family of genes/proteins. Suberites domuncula is a member of the most ancient and simplest extant phylum of multicellular animals – Sponges (Porifera). Database of S. domucula expressed sequence tags (ESTs) was recently constructed by random cDNA sequencing. Herein we report new evidence on sponge Suberites domuncula NDPK/Nm23. The sponge protein was named Nm23-SD1, because it displays the highest sequence similarity with human Nm23-H1 protein. The overall sequence homology of Nm23-SD1 and human Nm23-H1 is very high - 79% (71% identity). The secondary structure prediction for sponge and human Nm23 protein pair is almost identical. Sponge Nm23-SD1 protein is more similar to mammalian/human Nm23-H1 protein than to most known Nm23 proteins from invertebrates. Further, sponge nm23-SD1 gene has three introns of which the first two are on the same positions as the human introns. Nm23-SD1 gene probably reflects the archetype of the metazoan NDP kinase gene. The goal of this study was to reveal the characteristics of the sponge gene/protein and discover whether the sponge Nm23-SD1 can replace the antimetastatic function of the human homolog in human metastatic breast cancer cell line MDA-MB-231T. Nm23-SD1 gene was cloned and overexpressed using pET15b and E. coli as a host. Purified protein showed nonspecific DNA-binding activity and has a similar level of kinase activity as its human homolog. The preliminary results reveal that the sponge Nm23-SD1 might have a similar cellular localization as the human Nm23-H1. Stable clones expressing sponge Nm23-SD1 are currently under construction.

nm23 kinase; sponge; evolution; nm23-H1

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