The Drosophila yolkless gene encodes a vitellogenin receptor belonging to the low density lipoprotein receptor superfamily.

Sequence comparisons of vitellogenins from a wide range of organisms have identified regions of similarity not only to each other but also to vertebrate apolipoproteins (e.g. apoB-100 and apoE). Furthermore, the chicken vitellogenin receptor, which also binds apolipoproteins receptor (LDLR) superfamily [Bujo, H., Hermann, M., Kaderli, M. O., Jacobsen, L., Sugawara, S., Nimpf, J., Yamamoto, T. & Schneider, W. J. (1994) EMBO J. 13, 5165-5175]. The yolk proteins of higher dipterans are exceptional, however, and instead show similarity to lipoprotein lipases. The molecular characterization of the putative Drosophila melanogaster vitellogenin receptor gene, yolkless (yl), described in this report reveals that the protein it encodes (Yl), is also a member of the LDLR superfamily. The ovary-specific 6.5-kb yl RNA codes for a protein of approximately 210 kDa which contains all three motifs common to the LDLR class of proteins. Within this superfamily, Yl may be related more to the LDLR-related proteins (LRPs), which bind both apolipoproteins and lipoprotein lipases. The similarity of Yl to the other LDLR proteins is restricted to the putative extracellular domain. Most noticeably, the cytoplasmic domain of Yl lacks the typical NPXY sequence which is involved in receptor internalization.     

Two distinct gene subfamilies within the family of cysteine protease genes.

A cDNA clone for a physiologically regulated Tetrahymena cysteine protease gene was sequenced. The nucleotide sequence predicts that the clone encodes a 336-amino acid protein composed of a 19-residue N-terminal signal sequence followed by a 107-residue propeptide and a 210-residue mature protein. Comparison of the deduced amino acid sequence of the protein with those of other cysteine proteases revealed a highly conserved interspersed amino acid motif in the propeptide region of the protein, the ERFNIN motif. The motif was present in all of the cysteine proteases in the data base with the exception of the cathepsin B-like proteins, which have shorter propeptides. Differences in the propeptides and in conserved amino acids of the mature proteins suggest that the ERFNIN proteases and the cathepsin B-like proteases constitute two distinct subfamilies within the cysteine proteases.     

Molecular cloning of a gene belonging to the carcinoembryonic antigen gene family and discussion of a domain model.

Carcinoembryonic antigen (CEA) is a glycoprotein important as a tumor marker for colonic cancer. Immunological and biochemical studies have shown it to be closely related to a number of other glycoproteins, which together make up a gene family. We have cloned a member of this gene family by using long oligonucleotide probes (42-54 nucleotides) based on our protein sequence data for CEA and NCA (nonspecific cross-reacting antigen) and on human codon usage. The clone obtained (lambda 39.2) hybridizes with six probes and has a 15-kilobase insert. The 5' end of the gene is contained within a 2700-base-pair EcoRI fragment, which hybridizes with five of the six synthetic probes. Sequencing of the 5' end region revealed the location and structure of one exon and two putative intron boundaries. The exon encodes part of the leader sequence and the NH2-terminal 107 amino acids of NCA. Southern blot analysis of human normal and tumor DNA, using as probes two lambda 39.2 fragments that contain coding sequences, suggests the existence of 9-11 genes for the CEA family. One of the restriction fragments described here has been used by Zimmermann et al. [Zimmermann, W., Ortlieb, B., Friedrich, R. & von Kleist, S. (1987) Proc. Natl. Acad. Sci. USA 84, 2960-2964] to isolate partial cDNA clones for CEA. The identity of this clone was verified with our protein sequence data [Paxton, R., Mooser, G., Pande, H., Lee, T.D. & Shively, J.E. (1987) Proc. Natl. Acad. Sci. USA 84, 920-924]. We discuss a domain structure for CEA based on the CEA sequence data and the NCA exon sequence data. It is likely that this gene family evolved from a common ancestor shared with neural cell adhesion molecule and alpha 1 B-glycoprotein and is perhaps a family within the immunoglobulin superfamily.     

The bat gene of Halobacterium halobium encodes a trans-acting oxygen inducibility factor.

Oxygen and light affect the expression of the bacterioopsin gene (bop), which encodes a light-driven proton pump in the purple membrane of Halobacterium halobium. This response is thought to be mediated by a set of genes located adjacent to the bop gene. DNA fragments containing either the bop gene or the entire bop gene cluster reversed the phenotype of purple membrane-deficient strains with mutations in the bop gene. Purple membrane synthesis was constitutive in one of these strains transformed with the bop gene alone. The same strain transformed with the bop gene cluster was inducible by low oxygen tension. Moreover, another strain that constitutively expresses purple membrane remained constitutive when transformed with the bop gene alone but the phenotype of the strain changed to inducible when transformed with the bop gene cluster. Additional experiments have confirmed that one of the genes of the bop gene cluster, the bat gene, encodes a trans-acting factor that is necessary and sufficient to confer inducibility of purple membrane synthesis by low oxygen tension.     

An erythrocyte-specific DNA-binding factor recognizes a regulatory sequence common to all chicken globin genes.

We have identified a protein present only in erythroid cells that binds to two adjacent sites within an enhancer region of the chicken beta-globin locus. Mutation of the sites, so that binding by the factor can no longer be detected in vitro, leads to a loss of enhancing ability, assayed by transient expression in primary erythrocytes. Binding sites for the erythroid-specific factor (Eryf1) are found within regulatory regions for all chicken globin genes. A strong Eryf1 binding site is also present within the enhancer of at least one human globin gene, and proteins from human erythroid cells (but not HeLa cells) bind to both the chicken and the human sites.