We report the 9210 bp sequence from a segment of yeast chromosome III cloned from strain AB972 in lambda PM3270. Analysis of this sequence and its comparison with the one derived from the corresponding segment of strain XJ24-24A revealed that the AB972 region contains a duplication of about 2 kb and a Ty element, which are not found in XJ24-24A and cause a quite significant rearrangement of the whole region. We performed functional analysis of YCR28, the largest open reading frame we found in both AB972 and XJ24-24A. YCR28 encodes a putative protein of 512 amino acids with some similarities to yeast allontoate permease. Its disruption does not cause any detectable phenotype on rich medium or on allantoate medium, while we observed a strain-dependent effect on sensitivity to amino acid balance and to 3-aminotriazole, when cells were grown in synthetic medium.