The Noc1-4p proteins were previously reported to be involved in intranuclear and nucleocytoplasmic transport of pre-ribosomes. Using fold recognition and structural modeling, we show that Noc1-4p are largely comprised of alpha-helical repeats similar to HEAT repeats. Because other HEAT-repeat proteins play key roles in transport processes, this finding provides a plausible mechanistic explanation for the function of the Noc proteins.