Kolb A, Hermoso J M, Thomas J O, Szer W
Proc Natl Acad Sci U S A. 1977 Jun;74(6):2379-83. doi: 10.1073/pnas.74.6.2379.
The presence of ribosomal protein S1 in 30S ribosomes is indispensable for the formation of 30S initiation complexes with natural mRNA. The 30S subunits lacking S1 retain activity with AUG as mRNA and are also active in poly(rU)-directed binding of Phe-tRNA. Isolated protein S1 stoichiometrically disrupts the secondary structure of helical and stacked single-stranded polynucleotides and converts them into their fully or partially denatured forms. A mono-N-ethylmaleimide derivatives of S1 is nearly devoid of any RNA helix-unwinding properties but is readily incorporated into 30S subunits deficient in S1. The resulting N-ethylmaleimide-S1-containing 30S subunits are completely inactive in the binding of MS2 [3H]RNA and in the formation of an initiation complex with MS2 RNA as mRNA. They retain activity in the binding of the initiator fMet-tRNA in response to the trinucleotide AUG and in the binding of Phe-tRNA in response to poly(U). They also retain the capacity to bind 50S subunits and to form 70S couples. These results suggest that a correlation exists between the RNA helix-unwinding capacity of isolated S1 and the function of S1 in the ribosomal binding of natural mRNA when the protein becomes part of the 30S subunit.
30S核糖体中核糖体蛋白S1的存在对于与天然mRNA形成30S起始复合物是必不可少的。缺乏S1的30S亚基对以AUG作为mRNA仍具有活性，并且在聚（rU）指导的苯丙氨酰 - tRNA结合中也具有活性。分离出的蛋白S1按化学计量破坏螺旋状和堆积的单链多核苷酸的二级结构，并将它们转化为完全或部分变性的形式。S1的单 - N - 乙基马来酰亚胺衍生物几乎没有任何RNA解旋特性，但很容易掺入缺乏S1的30S亚基中。所得含N - 乙基马来酰亚胺 - S1的30S亚基在结合MS2 [3H]RNA以及以MS2 RNA作为mRNA形成起始复合物方面完全无活性。它们在响应三核苷酸AUG时结合起始甲硫氨酰 - tRNA以及在响应聚（U）时结合苯丙氨酰 - tRNA方面仍具有活性。它们还保留了结合50S亚基并形成70S复合物的能力。这些结果表明，当该蛋白成为30S亚基的一部分时，分离出的S1的RNA解旋能力与S1在核糖体结合天然mRNA中的功能之间存在相关性。
