Friday, October 5, 2012

How can a virus see?

Proteorhodopsin genes in giant viruses

This is teh awesome! Rhodopsin is a key protein used in the eye, the first step in capturing light and turning it into sensory information. It can be found even in single celled creatures that swim towards or away from light as a feeding signal. Here, the virus is modifying the behavior of the infected cell with its own rhodopsin gene.

There are many examples of parasites modifying the behavior of their host. A creepy example (aren't all parasites creepy?) is the fungus that makes zombie ants leave their nest and climb up where they will get eaten, which helps the fungus spread.

So how do these giant viruses see with their rhodopsin gene? By making their host see for them. Giant viruses are very different from very small viruses, like the famous Ebola virus. Ebola is less than 20,000 nucleotides long (single stranded RNA) and makes only eight proteins, according to Wikipedia. In contrast, mimivirus has a genome of almost 1.2 million base pairs of DNA. While Ebola just replicates as fast as possible before destroying the host cell, giant viruses are more long lived parasites.

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