ABSTRACT
ABSTRACT: Special regions in protein sequences with biased compositions of amino acids beyond restricted criteria are simply defined as “unusual sequences.” The presence of these unusual sequences has shown not rare and of great importance in human diseases. The present work reviewed the distribution, abundance, structure, and functional features of these unusual sequences with an emphasis on polyQ, polyA, Leu-rich, and tryptophan-aspartic acid (WD) repeats and their association with human diseases as well as other relevant medical significance.
