Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P11021 (BiP)
 2,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Type I signal-anchor sequences mediate translocation of the N-terminal domain (N-domain) across the endoplasmic reticulum (ER) membrane. To examine the translocation in detail, dihydrofolate reductase (DHFR) was fused to the N-terminus of synaptotagmin II as a long N-domain. Translocation was arrested by the DHFR ligand methotrexate, which stabilizes the folding of the DHFR domain, and resumed after depletion of methotrexate. The targeting of the ribosome-nascent chain complex to the ER requires GTP, whereas N-domain translocation does not require any nucleotide triphosphates. Significant translocation was observed even in the absence of a lumenal hsp70 (BiP). When the nascent polypeptide was released from the ribosomes after the membrane targeting, the N-domain translocation was suppressed and the nascent chain was released from the translocon. Ribosomes have a crucial role in maintaining the translocation-intermediate state. The translocation of the DHFR domain was greatly impaired when it was separated from the signal-anchor sequence. Unfolding and translocation of the DHFR domain must be driven by the stroke of the signal-anchor sequence into translocon.
 ...
PMID:Translocation of a long amino-terminal domain through ER membrane by following signal-anchor sequence. 1610 79

The production of human monoclonal antibodies for therapeutic use is of increasing importance for treatment of viral infections such as AIDS. As human x mouse heterohybridomas rarely reach the growth rates and cell specific production rates of mouse hybridomas the transfection of standard cell lines, such as CHO or BHK, is a promising alternative. This has the additional advantage that the IgG subtype can be changed to suit the desired application. However, the use of a cell line that has not originally developed to produce antibodies, as lymphocytes and myeloma cells have, might have unrecognised drawbacks. This will be especially significant in the case of antibodies as each molecule consists of 4 chains linked by disulphide bonds which require specific intracellular factors to be properly folded and processed (Heavy chain binding protein, Protein Disulfide Isomerase a.o.). In this study we have therefore compared two cell lines: a human x mouse heterohybridoma producing IAM-2F5, a human IgG(3) antibody specific for HIV-1 with neutralising properties and a Chinese Hamster Ovary cell transfected with dihydrofolate reductase and with the heavy and light chain genes of IAM-2F5 modified to IgG(1). From each cell line three subclones were selected with low, medium and high specific production rates. Batch cultures were performed and the following cellular parameters analysed by flow cytometry; 1) total RNA content (translational activity); 2) total protein content; 3) cell cycle phase distribution; 4) concentration of light and heavy chains; 5) concentration of helper proteins such as BiP and PDI. The production rate of heterohybridoma cells was best reflected in the intracellular concentration of kappa chain, while the gamma chain concentration was comparable for all three subclones. In the CHO cells the gamma chain expression and thus gene copy number appeared to be the limiting factor. The GRP78/BiP concentration in CHO remained unchanged in spite of a 5-fold higher concentration of gamma chain in the high producing subclone. The PDI concentration in CHO cells was much lower compared to the heterohybridoma cells, irrespective of production rates.
 ...
PMID:Comparison of the production of a human monoclonal antibody against HIV-1 by heterohybridoma cells and recombinant CHO cells: A flow cytometric study. 2235 23