RESUMO
Genome sequencing projects are predicting large numbers of novel proteins, whose interactions with other proteins must mediate the function of cellular processes. To analyse these networks, we used the yeast two-hybrid system on a genome-wide scale to identify 25 interactions among the proteins of Escherichia coli bacteriophage T7. Among these is a set of six interactions connecting proteins that function in DNA replication and DNA packaging. Remarkably, two genes, arranged such that one entirely overlaps the other and uses a different reading frame, encode interacting proteins. Several of the interactions reflect intramolecular associations of different domains of the same polypeptide, suggesting that the two-hybrid assay may be useful in the analysis of protein folding. This global approach to protein-protein interactions may be applicable to the analysis of more complex genomes whose sequences are becoming available.
Assuntos
Bacteriófago T7/ultraestrutura , Proteínas Virais/metabolismo , Sequência de Aminoácidos , Bacteriófago T7/química , Bacteriófago T7/genética , Sequência de Bases , Primers do DNA/química , Replicação do DNA , Homologia de Genes , Vetores Genéticos , Substâncias Macromoleculares , Dados de Sequência Molecular , Ligação Proteica , Proteínas Recombinantes/metabolismo , Proteínas Virais/genética , Replicação ViralRESUMO
In patients with acquired immunodeficiency syndrome (AIDS), mycobacterial diseases are leading opportunistic infections. The reasons for the peculiar propensity for disseminated infection with Mycobacterium avium complex (MAC) remain unclear. We have previously examined, in detail, the ability of monocytes from healthy donors to take up and kill MAC under both nonopsonic and opsonic conditions. We have now evaluated the in vitro ability of peripheral blood monocytes from HIV(+) patients to take up and kill MAC organisms, and have discovered a reduced ability under both nonopsonic and opsonic conditions. This reduction is due to: 1) apparent defect(s) in the phagocytes themselves, and 2) substance(s) in the HIV(+) serum which actively suppresses phagocyte activity.
Assuntos
Atividade Bactericida do Sangue , Soropositividade para HIV/sangue , Soropositividade para HIV/microbiologia , Monócitos/microbiologia , Complexo Mycobacterium avium/imunologia , beta-Glucanas , Adulto , Atividade Bactericida do Sangue/efeitos dos fármacos , Células Cultivadas , Feminino , Glucanos/farmacologia , Soronegatividade para HIV , Humanos , Masculino , Pessoa de Meia-Idade , Monócitos/virologiaRESUMO
The uptake of Mycobacterium avium complex (MAC) microorganisms by human peripheral blood monocytes (PBMs) and alveolar macrophages (AMs) is not well understood. We have previously shown, under opsonic conditions, that humoral factors are important in mediating the uptake of MAC by PBMs. However, the receptor-ligand interactions occurring under nonopsonic conditions remain unclear. We compared the uptake of untreated human PBMs and AMs in a serum-free medium with phagocytes treated to remove surface receptors. Removal of complement receptors CR1 and CR3, the Fc receptor (FcR), and the transferrin receptor (TfR) resulted in significantly lower levels of MAC uptake in serum-free medium by both PBMs and AMs. The addition of barley beta-glucan or mannan from Saccharomyces cerevisiae inhibited MAC uptake by untreated phagocytes in a dose-dependent manner. MAC uptake by PBMs or AMs was never completely abrogated by combining treatments (removal of CR1, CR3, FcR, and TfR and adding mannan or beta-glucan), indicating still-unknown mechanisms of uptake under nonopsonic conditions. We conclude that CR1, CR3, FcR, TfR, the mannose receptor, and possibly a separate beta-glucan-inhibitable receptor all may be involved in nonopsonic uptake of MAC by both PBMs and AMs.
