Molecular cloning and protein folding characterization of a predicted heme-binding globin in a sugar cane EST database.

Abstract

A very large and representative sugar cane expression sequence tag (EST) library (SUCEST) was sequenced by a Brazilian consortium, opening the possibility to study important proteins, such as hemoglobins, which are largely present across the plant kingdom. e widespread presence and long evolutionary history of plant hemoglobins suggest a major role for this protein family in plants; however, little is known about their functional roles. In this study, we report the identi cation and characterization of a putative non-symbiotic hemoglobin cDNA clone that was identi ed in SUCEST. e cDNA was cloned, and the recombinant protein was puri ed and folded, as shown by its circular dichroism and emission uorescence spectra. e expressed globin protein was able to bind hemin, as a characteristic Soret band was observed in the absorbance spectrum and increases were seen in the amount of secondary structure and in the stability of the protein. A model for the structure of the sugarcane hemoglobin was created using the crystal structure of a rice hemoglobin, and this model showed a conserved globular conformation.