HspB3, the most deviating of the six known human small heat shock proteins.
From the alignment of 14 EST clones, the cDNA sequence of a novel human small heat shock protein (sHsp), called HspB3, could be deduced. The 3' part of the HspB3 cDNA is 99% identical to that of the previously reported HspL27 cDNA (W.Y. Lam, S.K. Wing Tsui, P.T. Law, S.C. Luk, K.P. Fung, C.Y. Lee, M.M. Waye, Isolation and characterization of a human heart cDNA encoding a new member of the small heat shock protein family-HSPL27, Biochim. Biophys. Acta 1314 (1996) 120-124). We argue that the HspB3 cDNA sequence is a corrected version of the HspL27 cDNA. The HspB3 cDNA is 742 bp long and contains an open reading frame specifying a polypeptide of 150 amino acid residues. Among the six known human sHsps it is evident that HspB3 is the most deviating one, having a unique N-terminal domain and essentially lacking a C-terminal extension. Northern blot analysis shows that in smooth muscle tissue the cDNA hybridizes with mRNA of about 0.9 kb.