Son H J, Cook G A, Hall T, Donelson J E
Department of Biochemistry, University of Iowa, Iowa City 52242.
Mol Biochem Parasitol. 1989 Feb;33(1):59-66. doi: 10.1016/0166-6851(89)90042-x.
Upstream of at least some telomere-linked genes for the variant surface glycoproteins (VSGs) of African trypanosomes are expression site associated genes (ESAGs) whose transcription is co-ordinated with the transcription of the adjacent VSG gene [Cully et al. (1985) Cell 42, 173-182]. The function of the corresponding ESAG proteins is not known. Here we show the sequences of two members of the ESAG-I family that are upstream of the VSG genes expressed in metacyclic variant antigen types 4 and 7 of Trypanosoma brucei rhodesiense. The corresponding metacyclic ESAG-I proteins of about 330 amino acids display extensive positional identity both with each other and with two other ESAG-I proteins of Trypanosoma brucei brucei. Only about 7% of the positions are occupied by a different amino acid in each of the four putative ESAG proteins while 40% of the positions are identical. Thus, the ESAG-I proteins are much more highly conserved than are the VSGs studied to date.
在非洲锥虫的至少一些与端粒相连的可变表面糖蛋白（VSG）基因的上游，是表达位点相关基因（ESAG），其转录与相邻VSG基因的转录协调进行[Cully等人（1985年），《细胞》42卷，173 - 182页]。相应ESAG蛋白的功能尚不清楚。在此，我们展示了在罗德西亚布氏锥虫的4型和7型循环后期可变抗原类型中表达的VSG基因上游的ESAG - I家族的两个成员的序列。相应的约330个氨基酸的循环后期ESAG - I蛋白彼此之间以及与布氏布氏锥虫的另外两个ESAG - I蛋白都显示出广泛的位置一致性。在这四个推定的ESAG蛋白中，每个蛋白只有约7%的位置被不同的氨基酸占据，而40%的位置是相同的。因此，ESAG - I蛋白比迄今为止研究的VSG蛋白保守得多。
