KW, to answer your question directly, PR only has to do with inbound links. Keyword optimization has to do with the anchor text of the incoming links and the on-page copy and the way it is arranged. The rest of this discussion is really about the position of this site in the SERPS, which has to do with many factors, PR, inbound links, age of site, etc.
I know better not to screw around with google. But not to long ago I had 500,000 inbounds coming from one search engine sitepage.nl all were scraping or doing something with my site. So what I finally contacted the owner of this Dutch search engine and explained the problems possible outcomes. I requested he redirect these sites to mine. After days of debate He did. He could not do all of them because of the amount. But now the inbounds average around 20,000 and I got some free traffic to boot. This happened on yahoo only their drunken bot can’t figure this stuff out.