Leucine-Threonine Repeats in FANCA: Ancient Structural Support, Novel Discovery

FANCA, FA complementation group A, is a protein within the Fanconi anemia DNA repair pathway which interacts with thirty-six other proteins in the human body, according to BioGrid. In order to understand FANCA properly, I took the FASTA sequence of FANCA and calculated the Boman Index for it using the Radzicka-Wolfenden scores for each of the 1,455 amino acids within its configuration, which led to a calculation of 1.37134707904 kcal/mol – described as “moderate” protein-binding abilities. Calculation of FANCA's Boman Index by hand led to the discovery of a leucine-threonine repeat (L-T repeat), which appears sixteen times in Homo sapiens, seventeen times in Mus musculus, nine times in Xenopus laevis, and five times in Nymphon striatum. The L-T repeat is often accompanied by a pattern of amino acids which can be described as having an XX/XXX motif; for example, RR/RRR for arginine. At the same time, the motif of FFXHTLTQXLTXXPX is conserved across H. sapiens, M. musculus, and X. laevis, implying that this motif – which I call the Super Legendary Duplicate Motif of Legendary Awesomeness, or for short, the super duplicate motif, due to both the XX motif being present (FF) and the L-T repeat being duplicated – may be an ancient structural support.