The typographical corrections below were made to the article on the date noted. These changes have been incorporated in the article and the details are documented here.

13 March 1998:

In the caption of Figure 2, the GenBank accession number "AF049108" replaced the word "pending" for the nucleotide sequence.

15 March 1998:

In the caption of Figure 2, the GenBank accession number "2935716" replaced the word "pending" for the amino acid sequence.