Rhapidosomes from Aquaspirillum itersonii: disruption and subsequent renaturation and characterization of the component proteins

Abstract

Rhapidosomes, tubular proteinaceous microstructures found in a variety of bacteria and algae, are resistant to disruption by many denaturing agents. They have potential application as a biomaterial and may also serve as a model for the study of self-assembly. Several reagents were tested for their ability to disrupt rhapidosomes isolated from Aquaspirillum itersonii into their component proteins. Only treatments with 01 M hydrochloric acid and 6 M guanidinium hydrochloride were found to disrupt rhapidosomes. A protocol was developed to renature the disrupted component proteins using rapid dilution and subsequent dialysis of the residual guanidinium hydrochloride. The renatured proteins were shown to have secondary structure as determined by circular dichroism. Furthermore, upon renaturation the two component proteins interacted with each other to form a complex of molecular mass > 2500 kDa. This complex, which may be a precursor in the pathway to rhapidosome formation, is currently being used to study the self-assembly process of these unique structures in vitro.