Nucleotide sequence for STRING protein sequence
Google is not a bad resource for such a question.  

In this case I find that the Yeast Genome site has a button which returns the nucleotide sequence. You can select the genomic sequence for the locus or the coding (CDS) sequence. 

http://www.yeastgenome.org/cgi-bin/locus.fpl?locus=Q0010

They also give a link to NCBI at the bottom of the page.  I think the reason you were having such a hard time is that UniProt extracted the protein sequence from the mitochondrial genome record.  Like many genome ORF predictions, Q0010 does not seem to have a distinct nucleotide record assigned yet.  

Summary: 

In general  you can do a web search for the uniprot id to start.  In many cases, like this one you will find that the nucleotide seq is only a chromosomal sequence record.   Biodatabases are a bit of a maze - there are scores of them out there, you may find that someone has clipped the nucleotide sequence of the gene out, which is helpful if there are introns!