Sequence of a cDNA clone encoding the polysialic acid-rich and cytoplasmic domains of the neural cell adhesion molecule N-CAM.

Abstract

Purified fractions of the neural cell-adhesion molecule N-CAM from embryonic chicken brain contain two similar polypeptides (Mr, 160,000 and 130,000), each containing an amino-terminal external binding region, a carbohydrate-rich central region, and a carboxyl-terminal region that is associated with the cell. Previous studies indicate that the two polypeptides arise by alternative splicing of mRNAs transcribed from a single gene. We report here the 3556-nucleotide sequence of a cDNA clone (pEC208) that encodes 964 amino acids from the carbohydrate and cell-associated domains of the larger N-CAM polypeptide followed by 664 nucleotides of 3' untranslated sequence. The predicted protein sequence contains attachment sites for polysialic acid-containing oligosaccharides, four tandem homologous regions of polypeptide resembling those seen in the immunoglobulin superfamily, and a single hydrophobic sequence that appears to be the membrane-spanning segment. The cytoplasmic domain carboxyl terminal to this segment includes a block of approximately equal to 250 amino acids present in the larger but not in the smaller N-CAM polypeptide. We designate these the ld (large domain) polypeptide and the sd (small domain) polypeptide. The intracellular domains of the ld and sd polypeptides are likely to be critical for cell-surface modulation of N-CAM by interacting in a differential fashion with other intrinsic proteins or with the cytoskeleton.

Sequence of contactin, a 130-kD glycoprotein concentrated in areas of interneuronal contact, defines a new member of the immunoglobulin supergene family in the nervous system

“…Sequences of cell surface proteins that have recently been published, were placed into the laboratory data base and compared with the GP130 protein sequence using the Microgenie sequence analysis program (Queen and Korn, 1984). This comparison included members of the cadherin and immunoglobulin supergene families (E-cadherin: Nagafuchi et al, 1987;N-cadherin: Hatta et al, 1988;L-CAM: Gallin et al, 1987;N-CAM: Cunningham et al, 1987;Hemperley et al, 1986;Barthels et al, 1987;myelin-associated glycoprotein (MAG): Salzer et al, 1987;I-CAM: Simmons et al, 1988;Staunton et al, 1988;carcinoembryonic antigen: Zimmermann et al, 1987;Thompson et al, 1987;Oikawa et al, 1987). The analysis detected a significant similarity of the 130-kd protein with the neural cell adhesion molecule NCAM .…”

Determinants for glycophospholipid anchoring of the Saccharomyces cerevisiae GAS1 protein to the plasma membrane.

“…Although the structural requirements for processing remain unknown, three features may be important: a C-terminal sequence of minimal length and hydrophobicity (4, 11-13, * Corresponding author. 38,41,66,73), the absence of a potential cytoplasmic domain (3,5,30,31,59,69,71,72) and an acceptable anchor attachment site (52). Recently, evidence has been provided for the existence of a similar type of membrane anchor in the yeast Saccharomyces cerevisiae (16,17).…”

Four exons encode a 93-base-pair insert in three neural cell adhesion molecule mRNAs specific for chicken heart and skeletal muscle.

“…One of these mRNAs encodes a polypeptide that resembles the ssd chain of chicken N-CAM; the other mRNA is larger and is as yet uncharacterized. In the protein structure the MSD1 sequence is inserted midway between the last ofthe five immunoglobulin-like domains that make up the NH2-terminal portion of N-CAM (12) and the region of the molecule associated with the membrane. Its location suggests that the insert may be encoded by exons that are between the human equivalent of exons 12 and 13 in the chicken gene.…”