The Trypanosome Leucine Repeat Gene in the Variant Surface Glycoprotein Expression Site Encodes a Putative Metal-Binding Domain and a Region Resembling Protein-Binding Domains of Yeast, <i>Drosophila</i> , and Mammalian Proteins

Abstract

We have identified a new variant surface glycoprotein expression site-associated gene (ESAG) in Trypanosoma brucei, the trypanosome leucine repeat (T-LR) gene. Like most other ESAGs, it is expressed in a life cycle stage-specific manner. The N-terminal 20% of the predicted T-LR protein resembles the metal-binding domains of nucleic acid-binding proteins. The remainder is composed of leucine-rich repeats that are characteristic of protein-binding domains found in a variety of other eucaryote proteins. This is the first report of leucine-rich repeats and potential nucleic acid-binding domains on the same protein. The T-LR gene is adjacent to ESAG 4, which has homology to the catalytic domain of adenylate cyclase. This is intriguing, since yeast adenylate cyclase has a leucine-rich repeat regulatory domain. The leucine-rich repeat and putative metal-binding domains suggest a possible regulatory role that may involve adenylate cyclase activity or nucleic acid binding.