Calreticulin molecular evolution: a strong purifying and episodic diversifying selection result

Calreticulin (CRT) is a low molecular weight protein present in vertebrates, invertebrates and higher plants. Its multiple functions have been demonstrated. It plays an important role as a chaperone and Ca²⁺ buffer inside sarcoplasmic/endoplasmic reticulum (SR/ER), and outside the ER in many physiological/pathological processes. Recently it has been observed that CRT over-expression or its absence is linked to various pathological conditions, such as malignant evolution and progression, and these facts really increased its study interests. Using an evolution approach CRT was further characterized. Several Bayesian phylogenetic analyses were performed using coding and amino acid sequences. CRT molecular evolution was investigated for the presence of negative or/and positive selection using HyPhy package. The results indicated that the purifying selection might have operated over the whole CRT primary structure. Although, an episodic diversifying selection was also found on the analyzed CRT sequences.