Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A plasmid-encoded gene for a hybrid pre-protein containing most of the bovine prolactin signal peptide (SpPRL) fused to the mature sequence of yeast invertase (IVT) was expressed and the product was processed and secreted by yeast. However, the level of IVT activity was reduced about six-fold when compared to that obtained with the wild type (wt) invertase signal peptide (SpIVT). When the 5'-untranslated sequence of the hybrid mRNA was truncated by 29 nucleotides, a 2.5-fold increase in secreted IVT was observed. Replacement of the PRL codons with preferred yeast codons did not result in any improvement in the production of secreted IVT. An increase in IVT activity to the level observed with the wt SpIVT was obtained by replacement of the Gly residue located between the N terminus and the central lipophilic region of the SpPRL by Ala. Since this amino acid replacement results in a higher probability of the SpPRL assuming an alpha-helical conformation, it suggests that the secondary structure of this region is important in recognition by the yeast secretory apparatus.
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PMID:Changes in a mammalian signal sequence required for efficient protein secretion by yeasts. 218 92

Immunoglobulin heavy-chain binding protein (BiP, GRP-78) associates tightly in the endoplasmic reticulum (ER) with newly synthesized proteins that are incompletely assembled, have mutant structures, or are incorrectly glycosylated. The function of BiP has been suggested to be to prevent secretion of incorrectly folded or incompletely assembled protein, to promote folding or assembly of proteins, or to solubilize protein aggregates within the ER lumen. Here we examine the interaction of BiP with newly synthesized polypeptides in an in vitro protein translation-translocation system. We find that BiP forms tight complexes with nonglycosylated yeast invertase and incorrectly disulphide-bonded prolactin, but does not associate detectably with either glycosylated invertase or correctly disulphide-bonded prolactin. Moreover, BiP associates detectably only with completed chains of prolactin, not with chains undergoing synthesis. We conclude that BiP recognizes and binds with high affinity in vitro to aberrantly folded or aberrantly glycosylated polypeptides, but not to all nascent chains as they are folding.
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PMID:Heavy-chain binding protein recognizes aberrant polypeptides translocated in vitro. 312 63

Intestinal lactase activity is maintained at high levels in suckling rats during the first 2 wk after birth. When 12-day-old rat pups were either mother fed (MF) or artificially reared (AR) with natural rat milk or several artificial formulas, the small intestines had gained similar weight in all animal groups by 16 days except in AR rats fed a chemically defined formula. In the ileum, villus length was similar in MF and AR rats, but crypt depth was significantly higher in all groups of AR rats. Ileal absorptive cells in both MF and AR rats showed immature characteristics, including supranuclear vacuoles, apical tubular systems, and pinocytotic vesicles. Jejunal lactase specific activity and total intestinal lactase activity were significantly higher in AR rats fed rat milk than MF rats at 16 days. Ileal lactase specific activity was similar in these two animal groups. In contrast, AR rats fed artificial formulas supplemented with either glucose or lactose as the sole carbohydrate source exhibited significantly lower ileal lactase specific activity and total intestinal lactase activity than MF rats. Intestinal sucrase activity was prematurely elevated in all AR rats, even when fed natural rat milk. Addition of prolactin (3.3 micrograms/ml) to an artificial formula did not prevent the premature decrease in intestinal lactase specific and total activities in AR rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Rat milk maintains intestinal lactase activity in rat pups whereas artificial formulas do not. 393 Oct 42