Chameleon Sequences: Ordered or Disordered

Abstract

Chameleon seqeuences represent a class of sequences violating the important paradigm of molecular biology of one sequence-one structure. Chameleon sequences adopt two different structures in the same protein or in another protein. Why these short sequences are capable of changing their structure has remained unknown. We have examined some properties of chameleon sequences and compared them with those from intreinsically disordered regions of proteins and sequences with known unique secondary structure. Our results show that chameleon sequences have charge distributions very similar to ordered sequences. The GRAVY value of ordered sequences differ from that of intrinsically disordered sequences. Chameleon sequences have GRAVY values close to ordered sequences. A charge-hydropathy plot cleary demonstrated the distribution of ordered, chameleon, and intrinsically disordered regions of proteins. Here again, chameleon sequences placed themselves close to ordered sequences. A conformational analysis of chameleon sequences revealed slight deviations of dihedral angles from ordered sequence values. Based on our analysis we propose that chameleon sequences, with close distance to ordered sequences, have gained limited capability of changing their secondary structure under suitable conditions.