Unexpectedly high variability of the histone H4 gene in Leishmania

The sequence of the cDNA of the histone H4 gene of Leishmania tarentolae is reported herein. The predicted 100-amino-acid-long protein has the highest degree of identity with the histone H4 gene of L. infantum and shares with it a 5' region that shows a very low degree of identity with the corresponding region of histone H4 genes from other organisms. However, between these two genes is a 7.7% nucleotide difference that results in seven different amino acids, located in the 5', central, and 3' regions of the coding sequence. Such a divergence in the H4 gene, which is considered to be one of the most highly conserved genes, between closely related members of the genus Leishmania is unexpected and may reflect some unusual features of these important proteins in kinetoplastid flagellates.