Moonlighting Proteins: Old Proteins Learning New Tricks

When the human genome sequence became available, it was found to en-code far fewer proteins than expected for such a complex organism with many different cell types. It was found that one gene does not necessarily encode one protein with one function. There are several methods by which a gene can encode multiple functions, including alternative RNA splicing. More recently, it has become appa-rent that a protein may have the ability to ‘moonlight’, that is, to have multiple, and sometimes apparently unrelated, functions within one polypeptide chain, Moonlighting might be a general method to increase the number of protein functions that are encoded by the genome.