Human inter-alpha-trypsin inhibitor. Isolation and characterization of heavy (H) chain cDNA clones coding for a 383 amino-acid sequence of the H chain.

A cDNA library cloned in lambda gt 11 expression vector was screened with specific anti-inter-alpha-trypsin inhibitor (ITI) heavy (H) chain antiserum. Among seven positive clones selected, two overlapping clones were sequenced. The corresponding consensus sequence encompasses a stretch of bases with one single open reading frame, and the deduced amino-acid sequence displays no homology with the full length cDNA-deduced amino-acid sequence of ITI-light (L) chain. Furthermore, analysis of poly A+ mRNAs hybrid-selected by the corresponding cDNA from clone lambda gt11 revealed an immunoprecipitable polypeptide of Mr 91,000. Northern blot analysis showed a single population of mRNAs of 3.3 kb. These data provide new evidence for the presence of distinct H and L chains in the 180 kDa ITI molecule.