Crossed (evolutionary) signals?( What do humans and single-celled ch...)

What do humans and single-celled choanoflagellates have in common? More than you'd think. New research into the choanoflagellate genome shows these ancient organisms have similar levels of proteins that cells in more complex organisms, including humans, use to communicate with each other.

According to a paper published last week in the Proceedings of the National Academies of Sciences, these findings help confirm choanoflagellates' role as an evolutionary link between single-celled and multi-celled organisms. They also contend that these insights into the organism's genome may mean that the proteins used to help cells communicate may have other roles as well. The researchers are from the University of California, San Francisco and the European Molecular Biology Laboratory in Heidelberg, Germany.

Choanoflagellates, or at least their ancestors, have long been suspected as being the bridge between microorganisms with only one cell and metazoan, or multi-cellular organisms. There are many clues that lead to this conclusion, including the fact that choanoflagellates are similar to the individual cells in ocean sponges and unlike most other flagellates, they use their flagellate, or tail, to push themselves through water, rather than being pulled by it.

By analyzing the recently-sequenced choanoflagellate genome, the researchers discovered another similarity between choanoflagellates and most metazoans--their genetic code caries the markers of three types of molecules that cells use to achieve phospho-tyrosine signaling proteins.

Animals depend on tyrosine phosphorylation to conduct a number of important communications between their cells, including immune system responses, hormone system stimulation and other crucial functions. These phospho-tyrosine signaling pathways utilize a three-part system of molecular components to make these communications possible.

Tyrosine kinases (TyrK) 'write' messages between c
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