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Biomedical subjects

J N Feng

Publications and source records attributed to J N Feng.

9 recordsLinked to original sources
PubMed2004

Structural analysis of the epitopes on erbB2 interacted with inhibitory or non-inhibitory monoclonal antibodies.

erbB2 oncogene encodes a growth factor receptor. The overexpression of erbB2 was correlated with more aggressive tumors and a poorer prognosis. Some antibodies directed to this molecule have an antitumor effect in vivo, but some antibodies do not. In an attempt to understand the molecular basis of the anti-erbB2 antibody interaction with erbB2 ectodomain (ECD), we analyzed binding epitopes on erbB2 for inhibitory and non-inhibitory antibodies, Herceptin and HF by computer-guided protein engineering and site-directed mutagenesis. Two different interaction domains were identified by molecular docking, computer graphics and distance geometry method and confirmed through studies on a series of mutants of erbB2 ECD. Non-inhibitory antibody HF only recognized N-terminal portion of erbB2 ECD, but inhibitory antibody Herceptin bound to C-terminal portion of it exclusively. The region interacted with inhibitory antibody Herceptin can be an important target for anticancer therapies.

Antibodies, Monoclonal↗
PubMed1999

A trans-envelope protein complex needed for filamentous phage assembly and export.

Assembly and export of filamentous phage requires four non-capsid proteins: the outer membrane protein, pIV; the inner membrane proteins, pI and pXI; and a cytoplasmic host factor, thioredoxin. Chemical cross-linking of intact cells demonstrates a trans-membrane complex containing pI and pIV. Formation of the complex protects pI from proteolytic cleavage by an endogenous protease. This protection also requires pXI, which is identical to the C-terminal portion of pI. This indicates that pXI, which is required for phage assembly in its own right, is also part of the complex. This complex forms in the absence of any other phage proteins or the DNA substrate; hence, it represents the first preinitiation step of phage morphogenesis. On the basis of protease protection data, we propose that the preinitiation complex is converted to an initiation complex by binding phage DNA, thioredoxin and the initiating minor coat protein(s).

Bacteriophages↗
PubMed1997

A permeabilized cell system that assembles filamentous bacteriophage.

A permeabilized cell system has been developed that is capable of assembling filamentous phage only upon addition of exogenous thioredoxin. The in vitro system exhibits the same component requirements seen in vivo: functional thioredoxin, an intact packaging signal in the substrate DNA, and the assembly protein, pIV. This crude in vitro system is insensitive to inhibitors of protein or DNA synthesis, demonstrating that particle assembly uses components that had accumulated before cell permeabilization. The temporal separation of the synthetic period, during which phage proteins and DNA accumulate, from the assembly period enabled us to examine the energy requirement for assembly. We show here that ATP hydrolysis is required for filamentous phage assembly and that the proton motive force is also important.

Bacteriophages↗
PubMed1997

HIV-1 gp41 by a common immunological epitope induces increased levels of antibodies against human interferon-beta in HIV-1 positive individuals.

Based on our finding that a similar epitope exists between human IFN-beta (aa128-134) and HIV-1 gp41 (aa586-595), we examined 20 sera from healthy and 20 from HIV-1 infected individuals for IFN-beta antibody levels by ELISA. The levels of anti-IFN-beta antibody in sera from HIV-infected individuals were increased by about 160% in comparison with HIV-negative. We affinity-purified anti-gp41 antibodies from sera of HIV-1-infected individuals using rsgp41-sepharose column. One of three antibodies could recognize human IFN-beta in comparison with antibodies from serum of a healthy individual. A mouse antiserum to human IFN-beta recognized rsgp41 (recombinant soluble gp41 Env amino acid 539-684), while the normal mouse serum (pre-immune serum) did not bind to rspg41. These results indicate that a common immunological epitope exists between human IFN-beta and HIV-1 gp41. The sequence-similarity suggests that this common immunological epitope may be located in the region aa128-134 of human IFN-beta and the immunosuppressive domain (aa583-599) of HIV-1 gp41. The increased levels of antibodies against interferon-beta in HIV-1 positive individuals may be explained by a common immunological epitope on human IFN-beta and HIV-1 gp41.

Adult↗
PubMed1993

Tn7 transposition: target DNA recognition is mediated by multiple Tn7-encoded proteins in a purified in vitro system.

We have reconstituted the transposition of the bacterial transposon Tn7 into its specific insertion site attTn7 with four purified Tn7-encoded proteins, TnsA+TnsB+TnsC+TnsD, and ATP. TnsA+TnsB+TnsC form a "core" recombination machine that recognizes the transposon ends and executes DNA breakage and joining; TnsD specifically recognizes attTn7. TnsA+TnsB+TnsC are specifically targeted to attTn7 through the TnsD-dependent interaction of TnsC, a nonspecific DNA-binding protein, with attTn7. Recombination appears to be activated by the assembly of a nucleoprotein complex containing the DNA substrates and Tns proteins. We suggest that TnsC plays a central role in communication between the transposon and the target DNA, particularly in directing insertion away from DNAs already containing a copy of Tn7.

Adenosine Triphosphate↗
PubMed1993

Human toxicosis caused by moldy rice contaminated with fusarium and T-2 toxin.

This is the first report on human toxicosis in China caused by moldy rice contaminated with Fusarium and T-2 toxin due to heavy rainfall during rice harvest season. One hundred and sixty-five persons ate the moldy rice and ninety-seven persons fall ill of food poisoning. The incidence was 58.8% and latent period was 10-30 min. The chief symptoms were nausea, dizziness, vomiting, chills, abdominal distension, abdominal pain, thoracic stuffiness and diarrhea. The fungi isolated from the moldy rice were predominantly Fusarium heterosporum (F. heterosporum) and F. graminearum. T-2 toxin was found in these moldy rice and the highest level was 420 ppb. The chief causative agent of intoxication was T-2 toxin.

China↗
PubMed1992

[Food poisoning caused by mouldy rice contaminated with Fusarium and T-2 toxin].

An epidemic of food poisoning in human beings occurred in Tongxiang County, Zhejiang Province after eating mouldy rice contaminated with Fusarium and toxins. Continuous rainfall took place during the rice harvest season. The number of patients poisoned was 97, the rate of incidence was 58.8%. The incubation period was 10 to 30 minutes. The chief symptoms were nausea, dizziness, vomiting, chills, abdominal distension, abdominal pain and diarrhea. The fungi isolated from the mouldy rice were predominantly Fusarium heterosporum and F. graminearum. T-2 toxin was found in the mouldy rice and the highest content was 420 ppb.

China↗
PubMed1990

Study on BcII/St14 RFLPs in Chinese for DNA diagnosis for hemophilia A.

The BcII polymorphism within DXS52 (St14) was reported. It was composed of 4 allelic fragments, 4.0 kb, 3.3 kb, 3.0 kb and 2.3 kb. The frequency of these fragment were 0.09, 0.12, 0.44 and 0.35 respectively in the Chinese. The polymorphism provided the PIC of 0.66. DNA analysis of families with hemophilia A showed that the confidence of the RFLPs was the same as the TaqI/St14 RFLPs and for carrier detection the former is much better than that of the TaqI/St14 RFLPs.

China↗