Biomedical subjects

B Strobl

Publications and source records attributed to B Strobl.

21 records · Page 2Linked to original sources

PubMed1997

cDNA cloning and expression of secreted Xenopus laevis dipeptidyl aminopeptidase IV.

From a Xenopus laevis skin library a cDNA coding for dipeptidyl aminopeptidase IV (DPP IV) was isolated. The ORF codes for a protein with sequence similarity to DPP-IV-like proteins, including mammalian DPP IV and X. laevis fibroblast activation factor. In contrast to the membrane-bound mammalian enzymes, mature X. laevis DPP IV is a soluble secreted polypeptide. The frog enzyme possesses a cleavable signal sequence; the mature protein starts at Thr30 of the polypeptide predicted from the cDNA sequence. Expression of the cloned cDNA by recombinant vaccinia virus resulted in the formation of a protein with the expected molecular mass and substrate specificity. Recombinant DPP IV was present in high concentration in the supernatant of infected cells and exhibited enzymatic activity towards the synthetic substrate alanyl-prolyl-p-nitroanilide.

Amino Acid Sequence↗

PubMed1996

The lipocalin Xlcpl1 expressed in the neural plate of Xenopus laevis embryos is a secreted retinaldehyde binding protein.

The cellular and structural properties and binding capabilities of a lipocalin expressed in the early neural plate of Xenopus laevis embryos and the adult choroid plexus have been investigated. It was found that this lipocalin, termed Xlcpl1, binds retinal at a nanomolar concentration, retinoic acid in the micromolar range, but does not show binding to retinol. Furthermore, this protein also binds D/L thyroxine. The Xlcpl1 cDNA was expressed in cell culture using the vaccinia virus expression system. In AtT20 cells, Xlcpl1 was secreted via the constitutive secretory pathway. We therefore assume that cpl1 binds retinaldehyde during the transport through the compartments of the secretory pathway that are considered to be the storage compartments of retinoids. Therefore, cpl1-expressing cells will secrete the precursors of active retinoids such as retinoic acid isomers. These retinoids may enter the cytosol by diffusion or receptor-controlled mechanisms, as has been shown for exogenously applied retinoids. Based on these data, it is suggested that cpl1 is an integral member of the retinoid signaling pathway and, therefore, it plays a key role in pattern formation in early embryonic development.

Amino Acid Sequence↗

PubMed1993

The receptor-destroying enzyme of influenza C virus is required for entry into target cells.

The hemagglutinin-esterase (HE) protein of influenza C viruses possesses an acetylesterase activity, which appears essential for replication, as determined by reduced infectivity after inhibition of the viral enzyme [Vlasak et al., J. Virol. 63, 2056-2062 (1989)]. Analysis revealed the absence of virus-specific RNA and protein synthesis in infected cells after inhibition of the receptor-destroying enzyme. In addition, hemolytic activity was reduced after incubation of influenza C/JJ/50 virus with diisopropyl-fluorophosphate or 3,4-dichloro-isocoumarin. Further analysis revealed that inhibition of hemolysis depends on virus and erythrocyte concentrations. It is suggested that an active receptor-destroying enzyme is required for entry of influenza C virus into target cells at a step prior to fusion of the viral and cellular membrane. Our data indicate that cleavage of receptors bound to the HE protein is a prerequisite for the low pH-triggered conformational change required for fusion.

Acetylesterase↗