Thermal regulation of trypanosomatid Methyl-end fatty acid desaturases.

ALLOATTI, ANDRÉS; UTTARO, ANTONIO D.

Rosario

Congreso; XLII Reunión anual de la SAIB; 2006

We have previously characterized trypanosomatid desaturases involved in the conversion of oleoyl- to linoleoyl-moieties of phospholipids in the endoplasmic reticulum membrane of the parasites. Trypanosoma brucei and Leishmania major oleoyl desaturases share 56% of identity and 75% of similarity, and comparable percentage of conversion (in vivo) of 16:1 and 18:1 fatty acids to the 16:2 and 18:2 ones, when expressed in yeasts at 30 ºC. Interestingly, T. brucei desaturase showed an increased substrate conversion at lower temperatures, more significant for 16:1, whereas L. major enzyme appears to be insensible to temperature downshift. Analysis of primary structure for both enzymes revealed a conserved theoretical membrane topology and consensus sequences for the three clusters of histidines, presumed to be part of the active site. T. brucei desaturase presents a 29 aminoacids larger N-terminus when compared to the L. major desaturase, which appears to be exclusive to the trypanosome enzyme as judged after multialignment with numerous available sequences. Construction of truncated and chimeric desaturases between the orthologous genes allowed us to localize the region for thermal regulation on the first half of T. brucei desaturase, with components present in i) the proximal N-terminus and ii) the catalytic domain located between the first and second hydrophobic domains.