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 correspon ding region of histone H4 genes from other organisms. However, between thes e 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 sequ ence. Such a divergence in the H4 gene, which is considered to be one of th e most highly conserved genes, between closely related members of the genus Leishmania is unexpected and may reflect some unusual features of these im portant proteins in kinetoplastid flagellates.