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Two synthetic peptides containing amino acid sequences analogous to the envelope glycoprotein of human T‐lymphotropic virus (HTLV) type III (HTLV‐III) and lymphadenopathy associated virus (LAV) were produced and used to immunize rabbits. The subsequent rabbit antisera neutralized HTLV‐III infectivity in vitro. The two synthetic peptides corresponded to regions associated with the gp120 or gp41 subunits respectively, of human immunodeficiency virus (HIV). This data indicates that at least two neutralizing epitopes are present on the envelope glycoprotein of HIV and these epitopes are associated with two distinct virus envelope glycoproteins. Antisera generated against these peptides neutralized infectivity of two different isolates of HTLV‐III. The data is discussed in terms of possible strategy for developing an effective vaccine against the etiologic agents of acquired immune deficiency syndrome (AIDS).

The transport of proteins into the nucleus requires not only the presence of a nuclear transport signal on the targeted protein but also the signal recognition proteins and the nuclear pore translocation apparatus. Complicating the search for the signal recognition proteins is the fact that the nuclear transport signals identified share little obvious homology. In this study, synthetic peptides homologous to the nuclear transport signals from the simian virus 40 large T antigen, Xenopus oocyte nucleoplasmin, adenovirus EIA, and Saccharomyces cerevisiae MATh2 proteins were coupled to a UV-photoactivable cross-linker and iodinated for use in an in vitro cross-linking reaction with cellular lysates. Four proteins, p140, plOO, p70, and p55, which specifically interacted with the nuclear transport signal peptides were identified. Unique patterns of reactivity were observed with closely related pairs of nuclear transport signal peptides. Competition experiments with labeled and unlabeled peptides demonstrated that heterologous signals were able to bind the same protein and suggested that diverse signals use a common transport pathway. The subcellular distribution of the four nuclear transport signal-binding proteins suggested that nuclear transport involves both cytoplasmic and nuclear receptors. The four proteins were not bound by wheat germ agglutinin and were not associated tightly with the nuclear pore complex.Specific transport of proteins into the nucleus is an important requirement for the integrity of that organelle. Specificity requires the presence of both a nuclear transport signal and the cellular proteins that recognize that signal. Many nuclear transport signals have been defined by mutation and then by their ability as synthetic peptides (15,22) or as gene fusions (4,9,16,20,25,27,28,33,35,37,40) to direct nuclear localization of nonnuclear proteins. Unlike transport into the secretory pathway, nuclear transport allows movement without proteolytic removal of the signal, which permits repetitive transport of the protein. These signals are characteristically short amino acid sequences with a high number of basic residues. Variations in the number, the sequence, and the position of the nuclear transport signals have been shown to affect the rate of nuclear uptake (5, 10,22,23,36). There is no consensus nuclear transport signal, which is also the case for transport into the endoplasmic reticulum. Despite the lack of homology and apparent flexibility between nuclear transport signals, decreased transport efficiency occurs when key amino acids are varied (19,21,23). This combination of heterogeneity and stringency in nuclear transport signal sequences raises the question of what receptor flexibility and heterogeneity are needed for signal recognition.Nuclear transport occurs at nuclear pores, which create aqueous, octagonal channels in the double-membraned nuclear envelope (39). Pores restrict the movement of large proteins yet allow free diffusion of small proteins and macromolecules. Electron microscopic st...

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Cercopithecus aethiops (African Green monkey), a nonhuman primate species distributed throughout subsaharan Africa, has been shown to have high seroprevalence rates of antibodies to simian immunodeficiency virus (SIV), and therefore, has been proposed as a natural reservoir for immunodeficiency viruses. Our laboratories have isolated SIV-like viruses from two East African subspecies of C. aethiops designated grivet and vervet monkeys. Analysis of the structural proteins based on the molecular weights and immunologic cross-reactivity to the prototypic SIV(MAC), HIV-1, and HIV-2 isolates suggests that these viruses are distinctly different. Heterogeneity was observed in the molecular weights of the gag, pol, and env gene products between SIV isolates from vervets [SIV(AGM(VER))] and grivets [SIV(AGM(GRI))]. Phenotypically, SIV(AGM(VER)) isolates were distinguishable from SIV(AGM(GRI)) isolates by the apparent size difference of the major core antigen p24. All SIV(AGM(GRI)) and SIV(AGM(VER)) isolates were found to encode a transmembrane protein of approximately 40 kD (gp40) in contrast to gp32 of SIV(MAC). Furthermore, the transmembrane protein was shown to be encoded by the entire env open reading frame, unlike gp32 of SIC(MAC) or gp36 of SIV(AGM(TYO-1)). These data indicate that viruses from C. aethiops share common features with SIV(MAC) and HIV-1, but represent diverse SIV-like viruses which may vary according to subspecies and geographic location.