Identification of a novel human serpin gene; cloning sequencing and expression of leupin

A novel serpin gene has been isolated, cloned and sequenced. A PCR amplified fragment of the gene was originally identified from human genomic DNA, and the full-length cDNA was subsequently isolated from HeLa cells and sequenced. The novel serpin is very high in protein sequence similarity (91.8%) to the squamous cell carcinoma antigen (SCCA), but contains substantial differences in the reactive site loop sequence, including a different amino acid (leucine) in the P1 position. The gene product, named leupin, is expressed in HeLa cells, SKGIIIa cells and human placenta. The protein has a predicted M(r) of 44,857 and an isoelectric point of 6.04 which is consistent with the more acidic form of SCCA associated with squamous cell carcinomas.