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C Stephan

Publications and source records attributed to C Stephan.

64 records · Page 4Linked to original sources
PubMed1992

The pro-region of the yeast prepro-alpha-factor is essential for membrane translocation of human insulin-like growth factor 1 in vivo.

Four yeast secretion signals, the 19-amino-acid invertase signal sequence, the 17-amino-acid acid-phosphatase signal sequence, and the pre-sequence and prepro-sequence of prepro-alpha-factor have been used to look for the secretion of recombinant human insulin-like growth factor 1 (IGF1) from Saccharomyces cerevisiae. Only the prepro-sequence, often referred to as the alpha-factor leader and consisting of an N-terminal 19-amino-acid pre-sequence or signal sequence attached to a 66-amino-acid pro-region, permits secretion of IGF1. The signal sequences alone do not allow the translocation of IGF1 into the endoplasmic reticulum. This is evident from the fact that IGF1-like molecules, to which the signal sequences are still attached, accumulate intracellularly in the cytosol. Fusion of the pro-region of the alpha-factor leader to the C-terminus of the acid-phosphatase and invertase signal sequences allows IGF1 to be secreted once again. These results reveal the essential role of the pro-region of the alpha-factor leader in the secretion of IGF1 and indicate that it may have a function in guiding a nascent IGF1 polypeptide to a state in which translocation can occur.

Amino Acid Sequence↗
PubMed1992

A modified Kex2 enzyme retained in the endoplasmic reticulum prevents disulfide-linked dimerisation of recombinant human insulin-like growth factor-1 secreted from yeast.

The majority of the recombinant human insulin-like growth factor-1 (IGF1) molecules, secreted from yeast using the prepro sequence of the prepro-alpha-factor, are not active monomers but inactive, disulfide-linked dimers. The prepro sequence of the prepro-alpha-factor, usually referred to as the alpha-factor leader (alpha FL), consists of a pre or signal sequence and a proregion. After signal sequence removal during translocation into the endoplasmic reticulum (ER) the proregion is still attached to IGF1 when it folds to acquire a tertiary structure. Mature IGF1 is released only in a late Golgi compartment by the membrane-bound endoprotease Kex2p. We find that co-expression of a novel ER-retained Kex2p variant, soluble Kex2pHDEL, can prevent intermolecular disulfide bond formation between two IGF1 molecules, implying that the presence of the proregion during the folding of IGF1 in the ER could be a reason for disulfide-linked dimerisation. This result indicates that the proregion of the alpha FL may have a role in the folding of some heterologous proteins in yeast, and that the ER-retained Kex2p mutant could be used as a convenient tool to study the cellular function of the proregions present naturally in various eucaryotic precursor proteins.

Blotting, Western↗
PubMedDate not supplied

Accurate determination of cast weight for neonates with clubfoot.

The purpose of this study was to determine changes in cast weight during the first 48 hours after application so that the true weight of a neonate can be estimated without the need for removing the cast. Five types of cast materials were compared. Cast weight measurements were obtained before and after application and at intervals during 48 hours. Final cast weight averaged 107.5% of dry weight for plaster and 99% of dry weight for synthetic cast materials. For very low birth weight infants, the difference between the initial wet weight of plaster of Paris and its final dry weight may be significant for calculating drug and fluid dosages. The weight of an infant can now be calculated without the necessity of cast removal.

Casts, Surgical↗