Magor K E, Warr G W, Middleton D, Wilson M R, Higgins D A
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston 29425.
J Immunol. 1992 Oct 15;149(8):2627-33.
cDNA clones encoding the H chains of the 7.8S and 5.7S IgY of the White Pekin duck have been isolated and sequenced. The H chain of the 7.8S IgY possesses four C region domains and thus resembles the H chain of chicken IgY with which it shows, in the C region, 54% inferred amino acid sequence identity, and complete conservation of the C region cysteine and tryptophan residues. The H chain of the 5.7S IgY possesses only two C region domains, that are virtually identical to CH1 and CH2 of the 7.8S IgY H chain. Although Southern blot genomic analysis did not resolve whether the two transcripts encoding the H chains of the 7.8S and 5.7S IgY are derived from one or two H chain-encoding genes, the CH 1, 2, 3, and 4 exons are apparently colinear, and no evidence was found for a separate locus in which CH1 and 2 exons were present and CH3 and 4 exons were lacking. The VH domain-encoding sequences of the cDNA for the two IgY H chains showed high similarity in the inferred VH gene (93% nucleotide and 91% inferred amino acid identity) and in the inferred JH segment (89% nucleotide and 93% inferred amino acid identity) but low similarity in the D region (26% nucleotide and 7% inferred amino acid identity). Genomic Southern blot hybridization analysis showed multiple VH-hybridizing sequences represented on up to 20 restriction fragments.
已分离并测序了编码白来航鸭7.8S和5.7S IgY重链的cDNA克隆。7.8S IgY的重链具有四个恒定区结构域，因此类似于鸡IgY的重链，在恒定区，它们的推断氨基酸序列同一性为54%，并且恒定区半胱氨酸和色氨酸残基完全保守。5.7S IgY的重链仅具有两个恒定区结构域，实际上与7.8S IgY重链的CH1和CH2相同。尽管Southern印迹基因组分析未能确定编码7.8S和5.7S IgY重链的两个转录本是来自一个还是两个重链编码基因，但CH1、2、3和4外显子显然是共线的，并且没有发现存在CH1和2外显子而缺少CH3和4外显子的单独基因座的证据。两种IgY重链cDNA的可变区（VH）编码序列在推断的VH基因中显示出高度相似性（核苷酸同一性为93%，推断氨基酸同一性为91%），在推断的连接区（JH）片段中也显示出高度相似性（核苷酸同一性为89%，推断氨基酸同一性为93%），但在多样性区（D区）相似性较低（核苷酸同一性为26%，推断氨基酸同一性为7%）。基因组Southern印迹杂交分析显示，多达20个限制性片段上存在多个VH杂交序列。
