异嗪皮啶与人γ球蛋白相互作用研究(英文)

利用荧光光谱和FT-IR方法在体外研究了异嗪皮啶与人γ球蛋白(HGG)的相互作用,利用Sips和Gibbs-Helmholtz方程计算了不同温度下结合反应的亲和力常数和热动学参数,利用Docking方法研究了其相互作用模式.Sips图谱结果表明,异嗪皮啶与HGG之间主要存在两类结合位点,以及基于范德华力和氢键的非特异性的相互作用,而且结合反应是熵驱动的自发的放热结合过程.在297,303,310,317 K下的亲和力常数分别为10.708,9.152,7.084,5.386 L/mol.利用FT-IR光谱方法计算了在异嗪皮啶加入前后HGG二级结构的含量变化,结果表明加入异嗪皮啶后,蛋白质β结构含量降低,但是蛋白质典型的β-构型仍然保持.根据Forster能量转移理论,计算得到蛋白质色氨酸残基与异嗪皮啶的平均结合距离为3.57 nm.HGG可作为异嗪皮啶的体内转运蛋白.     

Peptide sequences of T-cell receptor delta and gamma chains are identical to predicted X and gamma proteins

Although most mature peripheral T lymphocytes express a major histocompatibility complex restricted, CD3-associated, antigen receptor (TCR) which has been well characterized, some T cells carry a different CD3-associated heterodimer on their surface. One of the two disulphide-linked chains of this putative second receptor, which in mice has relative molecular mass (Mr) 35,000 (35K), has been identified as a product of the group of gamma genes. The other chain, termed delta (Mr 45K in mice), is not as well characterized. Although gamma/delta-bearing cells are a minor subset among peripheral T lymphocytes, they are the only CD3+ cells in the thymus early in ontogeny. Taking advantage of these kinetics, we have generated gamma/delta-bearing hybridomas, using a new TCR alpha chain-negative variant of the AKR thymoma BW5147 as tumour parent, fetal thymocytes as normal cell partners, and an anti-CD3 monoclonal antibody (mAb) as screening reagent. Gamma and delta chains from one of these hybrids have been purified and partially sequenced. The sequences obtained indicate that delta is indeed identical to the polypeptide encoded by the recently described gene X, as suggested by Chien et al.     

Self-tolerance to transgenic gamma delta T cells by intrathymic inactivation

During their intrathymic differentiation, T lymphocytes expressing alpha beta T-cell receptors (TCR) are negatively and positively selected. This selection contributes to the establishment of self-tolerance and ensures that mature CD4+ and CD8+ cell populations are restricted by the self major histocompatibility complex. Little is known, however, about gamma delta T-cell development. To investigate whether selection operates in the establishment of the gamma delta T-cell class, we have generated transgenic mice using gamma- and delta-transgenes encoding a TCR that is specific for a product of a gene in the TL-region of the TLb haplotype. Similar numbers of thymocytes expressing the transgenic TCR were generated in mice of TLb and TLd haplotypes. But gamma delta thymocytes from TLb and TLd transgenic mice differed in cell size, TCR density and in their capacity to respond to TLb stimulator cells or interleukin-2 (IL-2). In contrast to gamma delta T cells from TLd transgenic mice, gamma delta T cells from TLb transgenic mice did not produce IL-2 and did not proliferate in response to TLb stimulator cells, but they did proliferate in the presence of exogenous IL-2. These results indicate that functional inactivation of self-antigen-specific T cells could contribute to the establishment of self-tolerance to thymic determinants.     

Human gamma delta+ T cells respond to mycobacterial heat-shock protein

Most T cells recognize antigen through the T-cell antigen receptor (TCR)alpha beta-CD3 complex on the T-cell surface. A small percentage of T cells, however, do not express alpha beta but a second type of TCR complex designated gamma delta (ref. 2). Unlike alpha beta+ lymphocytes, gamma delta+ lymphocytes do not generally express CD4 or CD8 molecules, and the nature of antigen recognition by these cells is unknown. To study antigen recognition by gamma delta+ lymphocytes we raised a gamma delta+ alpha beta- -CD4-CD8- line from an individual immune to PPD (purified protein derivative). This line showed a specific proliferative response to PPD and to a recombinant mycobacterial heat-shock protein (HSP) of relative molecular mass 65,000 (65K). The gamma delta+ line was shown to exhibit a major response to HSP in the presence of autologous antigen-presenting cells (APCs). Minor responses occurred, however, with APCs matched for some HLA class I or II antigens, whereas no response occurred with HLA-mismatched APCs. These findings, therefore, document the requirement of HSP-reactive gamma delta+ lymphocytes for histocompatible APCs.