Refined purification of large amounts of rat cvHsp/HspB7 and partial biological characterization in vitro

The cardiovascular heat shock protein (cvHsp/HspB7) exhibited cardiac-specific expression and is a possible candidate of dilated cardiomyopathy in heart failure. The molecular characteristics and biochemical properties of cvHsp are only partially understood. This study was aimed to identify the biological properties and molecular high-order structure of cvHsp. The cvHsp protein was prepared by the refined purification at large amount. The pooled fractions were existed as two types of oligomers in solution and exhibited chaperone-like activity. The circular dichroism analyzed ureainduced unfolding processes. Multiple sequence alignment and an automated protein modeling were used to describe the three-dimensional structural model of the cvHsp monomer and dimer. By the refined purification, the cvHsp appeared in oligomeric and dimeric forms (approximately 17 kDa and 40 kDa, respectively) composed of 18.6-kDa monomers. The cvHsp prevented dithiothreitol (DTT)-induced aggregation of the insulin B chain and conferred oligomeric unfolding process in urea-containing solution. It exhibited structural stability and conformed to the two-state folding/unfolding oligomerization model. According to sequence alignment of the rat cvHsp gene, three-dimensional model based on the crystallographic structure of wheat Hsp16.9 was reconstructed. The cvHsp presented two antiparallel β-sheet sandwich structure of sHsp' core α-crystallin domain, and formed dimeric or oligomeric organization in solution. This work described the structural components of cvHsp and existed as the polydispersed molecular oligomers in vitro, which are some common properties of the sHsp family. These characteristics of the cvHsp gene is helpful to clarify molecular functionality in cardiac diseases.