Biomedical subjects

J A Haefliger

Publications and source records attributed to J A Haefliger.

40 records · Page 3Linked to original sources

PubMed1987

Comparison of the organization and fine structure of a chicken and a Xenopus laevis vitellogenin gene.

The structural organization and the coding nucleotide sequence of the Xenopus laevis A2 and the chicken major vitellogenin genes have been compared. Both genes show the same exon-intron organization. However, the degree of homology between the nucleotide and derived amino acid sequences varies extensively along the genes. Several of the 35 exons are quite similar, and a unique cysteine motif in the lipovitellin II domain is conserved between the two genes. In contrast, one internal region is quite divergent. Part of this region encodes phosvitin, which appears to have evolved rapidly by both point mutations and duplications of serines or short other amino acid stretches. On the basis of these observations, we discuss the possible mechanism of evolution of phosvitin in vertebrates.

Amino Acid Sequence↗

PubMed1987

Precursor-product relationship between vitellogenin and the yolk proteins as derived from the complete sequence of a Xenopus vitellogenin gene.

In Xenopus laevis four estrogen-responsive genes are expressed simultaneously to produce vitellogenin, the precursor of the yolk proteins. One of these four genes, the gene A2, was sequenced completely, as well as cDNAs representing 75% of the coding region of the gene. From this data the exon-intron structure of the gene was established, revealing 35 exons that give a transcript of 5,619 bp without the poly A-tail. This A2 transcript encodes a vitellogenin of 1,807 amino acids, whose structure is discussed with respect to its function. At the nucleic acid as well as at the protein level no extensive homologies with any sequences other than vitellogenin were observed. Comparison of the amino acid sequence of the vitellogenin A2 molecule with biochemical data obtained from the different yolk proteins allowed us to localize the cleavage products on the vitellogenin precursor as follows: NH2 - lipovitellin I - phosvitin (or phosvette II - phosvette I) - lipovitellin II - COOH.

Amino Acid Sequence↗

PubMed1987

Complementary DNA cloning of complement C8 beta and its sequence homology to C9.

The complete amino acid sequence of mature C8 beta has been derived from the DNA sequence of a cDNA clone identified by expression screening of a human liver cDNA library. Comparison with the amino acid sequence of C9 shows an overall homology with few deletions and insertions. In particular, the cysteine-rich domains and membrane-inserting regions of C9 are well conserved. These findings are discussed in relation to a possible mechanism of membrane attack complex formation.

Amino Acid Sequence↗

PubMedDate not supplied

Structural and functional characterization of complement C8 gamma, a member of the lipocalin protein family.

Human complement component C8 exhibits an unusual structure in that it contains three chains, two of which, alpha and beta, display high sequence homology to other complement and CTL pore-forming proteins. The third chain, C8 gamma, is covalently linked to C8 alpha by a disulfide linkage; it is demonstrated that Cys40 of C8 gamma is linked to Cys164 of C8 alpha, a unique cysteine located in a loop located between the cysteine-rich LDL-receptor class A module and the membrane-inserting region of C8 alpha. C8 gamma was recently identified as a member of the lipocalin protein family, in which all proteins were either shown to, or are believed to bind small hydrophobic ligands. The present results now demonstrate that C8 gamma incorporates retinol and retinoic acid in the presence of 2 M NaCl. Molecular modeling of C8 gamma, based on the crystal structure of the homologous beta-lactoglobulin, reveals a structure of eight antiparallel beta-strands, bearing a highly hydrophobic binding pocket. The residues participating in the pocket formation are highly conserved when compared with the structures of beta-lactoglobulin and retinol-binding protein, both of which are known to interact with retinol. It is therefore proposed that C8 gamma may act as a retinol transporting protein in plasma.

Alpha-Globulins↗