Morlé L, Roux A F, Alloisio N, Pothier B, Starck J, Denoroy L, Morlé F, Rudigoz R C, Forget B G, Delaunay J
Centre National de la Recherche Scientifique (CNRS) URA 1171, Faculté de Médecine Grange-Blanche, Lyon, France.
J Clin Invest. 1990 Aug;86(2):548-54. doi: 10.1172/JCI114743.
Spectrin alpha I/74 elliptocytosis results from abnormalities involving the "head" region of spectrin dimer. Increased susceptibility to trypsin enhances cleavage of the alpha spectrin chain, yielding an increased amount of the alpha I 74-kD fragment at the expense of the alpha I 80-kD parent fragment. Recently we showed that the mutations causing the Sp alpha I/74 abnormality may lie in the alpha- or the beta-chain, and that spectrin Culoz and spectrin Lyon were two (alpha I/74) alpha-variants, respectively. We now show that the spectrin Culoz alpha I domain undergoes prominent tryptic cleavage after Lys 42, whereas cleavage prevails after Arg 39 in spectrin Lyon. Applying the polymerase chain reaction (PCR) technique to exon 2 of the spectrin alpha I domain, we have established that the mutation responsible for spectrin Culoz is alpha I 40 Gly----Val; GGT----GTT. Applying the PCR technique to the cDNA derived from reticulocyte mRNA, we have shown that the mutation responsible for spectrin Lyon is alpha I 43 Leu----Phe; CTT----TTT. Studies of normal controls and of family members using dot blot hybridization with allele-specific oligonucleotide probes confirmed these results. Variants such as spectrin Culoz and spectrin Lyon should provide insight into a region that participates in spectrin dimer self-association and whose susceptibility to proteolysis must reflect subtle conformational changes.
血影蛋白αI/74椭圆形红细胞增多症是由涉及血影蛋白二聚体“头部”区域的异常引起的。对胰蛋白酶敏感性增加会增强α血影蛋白链的裂解，导致αI 74-kD片段的量增加，而以αI 80-kD亲本片段为代价。最近我们发现，导致SpαI/74异常的突变可能位于α链或β链上，并且血影蛋白Culoz和血影蛋白Lyon分别是两种（αI/74）α变体。我们现在表明，血影蛋白Culoz的αI结构域在赖氨酸42之后会发生显著的胰蛋白酶裂解，而血影蛋白Lyon在精氨酸39之后裂解占主导。将聚合酶链反应（PCR）技术应用于血影蛋白αI结构域的外显子2，我们确定导致血影蛋白Culoz的突变是αI 40 Gly→Val；GGT→GTT。将PCR技术应用于源自网织红细胞mRNA的cDNA，我们表明导致血影蛋白Lyon的突变是αI 43 Leu→Phe；CTT→TTT。使用等位基因特异性寡核苷酸探针进行点杂交对正常对照和家庭成员的研究证实了这些结果。诸如血影蛋白Culoz和血影蛋白Lyon等变体应该能让我们深入了解参与血影蛋白二聚体自我缔合的区域，其对蛋白水解的敏感性必定反映了细微的构象变化。
