Protein secretion signal peptide

The rest of the known sequences of all four classes of BCB domain-containing proteins feature signal peptides in their precursors, indicating that they are translocated across the bacterial cytoplasmic membrane or are translated on the endoplasmic reticulum-bound ribosomes and sent to the secretory pathway in eukaryotes. Thus they are located in the bacterial periplasm, secreted into the extracellular milieu, or anchored to the cell surface. 

Secretion The majority of studies involving nonclassical delivery focus exclusively on the import process. The initial work in this field, however, involved proteins that were found to possess not only nonclassical import activity but also leaderless secretory activity (secretion in the absence of a secretion signal peptide or use of the Golgi apparatus). The mechanism of this type of secretion is no clearer than that of import in fact, it is uncertain at this time whether these mechanisms are even related, especially considering the asymmetry of the cell membrane. It seems reasonable to assume for experimental testing purposes, however, that the common... 

The protein contains an N-terminal signal peptide of 17 amino acid residues for secretion. The luminescence reaction of coelenterazine catalyzed by the recombinant luciferase shows a luminescence emission maximum at 485 nm, whereas the luminescence catalyzed by the native luciferase shows a maximum at 480 nm. 

Overexpression of apoaequorin (Inouye et al., 1989, 1991). To produce a large quantity of apoaequorin, an apoaequorin expression plasmid piP-HE containing the signal peptide coding sequence of the outer membrane protein A (ompA) of E. coli (Fig. 4.1.12) was constructed and expressed in E. coli. The expressed apoaequorin was secreted into the periplasmic space of bacterial cells and culture medium. The cleaving of ompA took place during secretion thus the... 

Albumin (69 kDa) is the major protein of human plasma (3.4-4.7 g/dL) and makes up approximately 60% of the total plasma protein. About 40% of albumin is present in the plasma, and the other 60% is present in the extracellular space. The liver produces about 12 g of albumin per day, representing about 25% of total hepatic protein synthesis and half its secreted protein. Albumin is initially synthesized as a preproprotein. Its signal peptide is removed as it passes into the cisternae of the rough endoplasmic reticulum, and a hexapeptide at the resulting amino terminal is subsequently cleaved off farther along the secretory pathway. The synthesis of albumin is depressed in a variety of diseases, particularly those of the liver. The plasma of patients with liver disease often shows a decrease in the ratio of albumin to globulins (decreased albumin-globuhn ratio). The synthesis of albumin decreases rela-... 

In some heterologous production systems, improper removal of the signal peptide may occur during the expression of secreted proteins, which would result in the addition or removal of amino acids at the N-terminal end. In most cases, these modifi-... 

Aside from the cysteine motif, conserved regions in the proteins encoded by WHnl.O and WHul.6 are likely to reflect functional roles. Based on the rules of Von Heijne (70), the N-terminal 16 amino acids may function as a signal peptide for secretion. Recombinant WHbl.O and WHt/1.6 proteins are secreted into the medium of infected insect cells (43)... 

Prepro proteins are synthesized with a signal peptide, which directs the protein to the endoplasmic reticulum, where the signal peptide is cleaved thereafter the propeptide is excized and the mature protein or peptide secreted into the circulation. 

Proteins that are destined to be secreted or to end up as transmembrane proteins are synthesized with an N-terminal signal peptide. Signal peptides are highly hydrophobic sequences of variable length. Proteins synthesized with signal peptides are termed preproteins. For example, insulin is a secreted protein. It is therefore synthesized as a preprotein. It is also synthesized in inactive form a proprotein. Insulin as initially synthesized is, in consequence, a preproprotein. 

Hemopexin was first identified as a heme binding P-globin in elec-trophoretograms of plasma of patients with hemolysis (17-19). The protein is synthesized and secreted by the liver (20-22), and during secretion the signal peptide is removed and the protein is glycosylated (23). Tissue forms of hemopexin are expected due to the presence of mRNA in brain (24), peripheral neurons (25), and neural retina (26), pointing to a function of hemopexin in barrier tissues. 

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