We have previously isolated several cDNA clones of mRNAs that have the unusual property of being localized to either the animal pole or the vegetal pole of frog eggs. To gain insight into the function of these maternal mRNAs we have determined their DNA sequence and deduced the sequence of the proteins they encode. Here we report that An2, an mRNA localized to the animal pole of Xenopus oocytes and eggs, codes for the alpha chain of mitochondrial ATPase. Furthermore, we compare the intracellular localization of the An2 mRNA and mitochondria in oocytes and eggs and find that they do not have the same degree of localization. In the light of these results we discuss possible reasons for the maternal localization of the An2 mRNA.