Fission yeast telomeric DNA sequence, SP4G4: 5'-(GGGGTTAC)(4)-3' has been reported to form the antiparallel tetraplex in the presence of K(+). We examined the structural properties of budding yeast telomeric DNA sequences, SCTELG4: 5'-(TGGGTGT G)(4)-3' and SCTELGG4: 5'-(TGGGTGTGG)(4)-3', in the presence of K(+). The major conformation of SCTELG4 and SCTELGG4 was a parallel tetraplex DNA. We also examined the interaction between tetraplex-binding ligand, TMPyP4, and each of the antiparallel tetraplex of SP4G4 and the parallel tetraplex of SCTELG4 and SCTELGG4. The ability of TMPyP4 to bind with all of the tetraplexes was observed. We conclude that TMPyP4 has the ability to bind with both the parallel and antiparallel tetraplex of the telomeric DNA sequences from budding and fission yeasts.