Sequence analysis of a cDNA clone encoding the liver cell adhesion molecule, L-CAM

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Liver cell adhesion molecule (L-CAM) mediates calcium-dependent adhesion in non-neural epithelial tissues.
• L-CAM is a cell surface glycoprotein with a mature form of Mr 124,000, synthesized as a Mr 135,000 precursor.

Purpose of the Study:

• To isolate and determine the nucleic acid sequence of a cDNA clone encoding chicken L-CAM.
• To elucidate the molecular structure and potential evolutionary origins of L-CAM.

Main Methods:

• Isolation and sequencing of a chicken L-CAM cDNA clone (lambda L320).
• Protein sequence analysis of L-CAM and its fragments.
• Bioinformatic analysis of the deduced amino acid sequence.

Main Results:

• The lambda L320 clone encodes a 2520-base-pair open reading frame and an 850-base-pair untranslated region.
• The deduced sequence includes a hydrophobic segment, confirming L-CAM as an intrinsic membrane protein.
• The mature L-CAM polypeptide consists of 727 amino acids (Mr 79,900 without carbohydrates) and contains three homologous internal segments, suggesting gene duplication.

Conclusions:

• The determined nucleic acid sequence provides a complete L-CAM precursor and mature cell surface sequence.
• L-CAM's unique sequence, lacking homology to N-CAM or immunoglobulin superfamily members, suggests a distinct evolutionary path.
• The presence of homologous segments points to a potential gene duplication event in L-CAM evolution.