Cloning and sequencing of the cDNA coding for pig pre-uteroglobin/Clara cell 10 kDa protein

Using reverse transcription-polymerase chain reaction (RT-PCR) on pig lung mRNAs, we have cloned and sequenced an almost full-length complementary DNA (cDNA) coding for pig pre-uteroglobin/Clara cell 10 kDa protein (UG/CC10), a major secretory protein of lung Clara cells. The deduced amino acid sequence indicated a preprotein of 91 residues, 21 of which corresponded to the signal peptide. Comparison of the sequence with those of known pre-UG/CC10 from other species indicated that the pig protein resembles the structure shared by human and Lagomorpha pre-UG/CC10 but differ from the proteins from Rodentia that are composed of 96 aminoacids and contain signal peptides of 19 residues. Some amino acids, that form part of a hydrophobic pocket inside the mature protein, are well conserved in all UG/CC10 suggesting an important function of this cavity. Northern analysis indicated that pig UG/CC10 mRNA is abundant in lung but is not detectable in liver, uterus or epididymis. The results are discussed in relation to a possible physiological function of UG/CC10.