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D Riemer

Publications and source records attributed to D Riemer.

27 records · Page 2Linked to original sources
PubMed1993

A nuclear lamin of the nematode Caenorhabditis elegans with unusual structural features; cDNA cloning and gene organization.

This report describes the characterization of the nuclear lamin CeLam-1 of the nematode Caenorhabditis elegans by molecular analysis of the corresponding complete cDNA and gene sequences. The primary structure of CeLam-1, representing only the third non-vertebrate lamin sequence currently known, follows essentially the features displayed by the B-type lamins of vertebrates and Drosophila. The nematode lamin shows, however, some exceptional properties. First, it lacks the SPTR sequence in front of the coil 1a domain which constitutes the major mitotic cdc2 kinase phosphorylation site. Second, two prominent deletions occur in the CeLam-1 sequence. One eliminates 14 amino acid residues from the coil 2 domain. A larger deletion of approximately 25 residues results in the shortest lamin tail domain documented so far. The latter corresponds to a region which varies considerably in sequence from highly acidic in vertebrate B-type lamins to rather basic in Drosophila lamin Dmo. CeLam-1 is encoded by a single 2.3 kb mRNA which is abundantly expressed in mixed-stage worm populations. The 5'-end of the mRNA is generated by trans-splicing to the SL1 leader sequence. The CeLam-1 gene extending over 2.7 kb is located on chromosome I. The gene is composed of 6 exons and 5 short introns, which all interrupt the coding sequence. Surprisingly, none of the intron positions has a counterpart in either the Drosophila lamin Dmo or the vertebrate lamin genes.

Amino Acid Sequence↗
PubMed1992

Analysis of the cDNA and gene encoding a cytoplasmic intermediate filament (IF) protein from the cephalochordate Branchiostoma lanceolatum; implications for the evolution of the IF protein family.

We report the molecular cloning of a full-length cDNA encoding a non-neuronal cytoplasmic intermediate filament (IF) protein of the cephalochordate Branchiostoma lanceolatum. Sequence and structural characteristics of IF-1 reveal a close relation to vertebrate IF proteins: they all lack the extended coil 1b version and the lamin tail homology found in protostomic IF proteins. This implies that divergence of type I to IV IF genes from a common ancestor either coincided with the origin of chordates or occurred at an earlier stage in the evolution of deuterostomes. The structural organization of the cephalochordate gene shows a closer relation to vertebrate type III genes than to type I or II genes. The single gene (approximately 19 kb) is composed of 7 exons and 6 introns which are all located within the sequence encoding the rod domain. The positions and phases of the introns show perfect homology to vertebrate type III genes. In line with the absence of protein sequence similarity of the tail domain, the Branchiostoma gene does not possess the introns interrupting this region in type III genes of vertebrates.

Amino Acid Sequence↗
PubMed1991

Cloning of the non-neuronal intermediate filament protein of the gastropod Aplysia californica; identification of an amino acid residue essential for the IFA epitope.

We describe the isolation and characterization of a full-length cDNA corresponding to the larger non-neuronal (nn) intermediate filament (IF) protein of the gastropod Aplysia californica. Comparison of the sequences of the nn-IF proteins from Aplysia californica and Helix aspersa shows a strong evolutionary drift. At a 72% sequence identity level, the IF proteins of Opisthobranchia and Pulmonata show a larger distance than vimentins from Xenopus and mammals. The sequence comparison of the two snail proteins provides an important step in understanding the epitope of the monoclonal antibody IFA mapped by previous studies to the consensus sequence at the carboxy-terminal end of the rod domain of IF proteins. We identify for the first time in a naturally occurring IF protein a single amino acid exchange which leads to the loss of the epitope. The consensus sequence YRKLLEGEE present in IFA-positive proteins such as the Helix IF protein is changed in the IFA-negative Aplysia protein only by the conservative substitution of the arginine (R) by a lysine (K). Thus, the IFA epitope is not a necessity of IF structure, and its presence or absence on different IF proteins reflects only small changes in an otherwise conserved consensus sequence. Consequently, lack of IFA reactivity does not exclude the presence of IF. This result predicts that IF are much more universally expressed in lower eukaryotes than currently expected from immunological results with the monoclonal antibody IFA.

Amino Acid Sequence↗
PubMed1990

Structure of an invertebrate gene encoding cytoplasmic intermediate filament (IF) proteins: implications for the origin and the diversification of IF proteins.

The structure of the single gene encoding the cytoplasmic intermediate filament (IF) proteins in non-neuronal cells of the gastropod Helix aspersa is described. Genomic and cDNA sequences show that the gene is composed of 10 introns and 11 exons, spanning greater than 60 kb of DNA. Alternative RNA processing accounts for two mRNA families which encode two IF proteins differing only in their C-terminal sequence. The intron/exon organization of the Helix rod domain is identical to that of the vertebrate type III IF genes in spite of low overall protein sequence homology and the presence of an additional 42 residues in coil 1b of the invertebrate sequence. Intron position homology extends to the entire coding sequence comprising both the rod and tail domains when the invertebrate IF gene is compared with the nuclear lamin LIII gene of Xenopus laevis presented in the accompanying report of Döring and Stick. In contrast the intron patterns of the tail domains of the invertebrate IF and the lamin genes differ from those of the vertebrate type III genes. The combined data are in line with an evolutionary descent of cytoplasmic IF proteins from a nuclear lamin-like progenitor and suggest a mechanism for this derivation. The unique position of intron 7 in the Helix IF gene indicates that the archetype IF gene arose by the elimination of the nuclear localization sequence due to the recruitment of a novel splice site. The presumptive structural organization of the archetype IF gene allows predictions with respect to the later diversification of metazoan IF genes. Whereas models proposing a direct derivation of neurofilament genes seem unlikely, the earlier speculation of an mRNA transposition mechanism is compatible with current results.

Amino Acid Sequence↗
PubMed1976

[Lipid mobilization in obesity without carbohydrate intolerance. 2. Caffeine-stimulated lipolysis].

The lipolysis induced by i.v. injection of caffeine (3 mg/kg body weight) has been investigated in 11 normal subjects and 18 obese patients with normal 50 g oral glucose tolerance test and normal thyroid-function. The pattern of blood-glucose and immunoreactive insulin (IRI) secretion were not influenced by caffeine in both groups. Both in the controls and obese group a significant response of FFA and glycerole were noted. In the obese group the caffeine-induced lipolysis was slightly higher as compared with controls. There are no differences in FFA-response between obese group and controls. The observations suggest that an impaired lipolysis is not a pathogenetic factor for development of obesity.

Adult↗