Liang S M, Thatcher D R, Liang C M, Allet B
J Biol Chem. 1986 Jan 5;261(1):334-7.
Human interleukin-2 (IL-2) has 3 cysteine residues; cysteines 58 and 105 form an intramolecular disulfide bridge, whereas cysteine 125 has a free sulfhydryl group. In this study, site-specific mutagenesis has been used to modify the cysteine residues of recombinant Escherichia coli-derived IL-2 (rIL-2) to evaluate the functional structure of IL-2. Substitution or deletion of cysteine 105 disrupted the disulfide bridge and yielded a mutant protein which was 8-10 times less active than wild type rIL-2. A similar modification at position 58, however, reduced the activity of rIL-2 by more than 250-fold. Although substitution of serine for cysteine 125 did not affect IL-2 activity, deletion of cysteine 125 or deletion of amino acids in the vicinity of this cysteine yielded mutant proteins with little, if any, activity. These results indicate that the protein structure in the vicinity of both positions 58 and 125 is more critical than that close to position 105. These findings may provide a clue to the understanding of the functional structure of human IL-2.
人白细胞介素-2（IL-2）有3个半胱氨酸残基；半胱氨酸58和105形成一个分子内二硫键，而半胱氨酸125有一个游离巯基。在本研究中，已使用位点特异性诱变来修饰重组大肠杆菌来源的IL-2（rIL-2）的半胱氨酸残基，以评估IL-2的功能结构。半胱氨酸105的取代或缺失破坏了二硫键，产生了一种突变蛋白，其活性比野生型rIL-2低8至10倍。然而，在位置58处进行类似修饰使rIL-2的活性降低了250倍以上。虽然用丝氨酸取代半胱氨酸125不影响IL-2活性，但缺失半胱氨酸125或缺失该半胱氨酸附近的氨基酸产生的突变蛋白几乎没有活性。这些结果表明，位置58和125附近的蛋白质结构比靠近位置105的结构更关键。这些发现可能为理解人IL-2的功能结构提供线索。
