Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 139

Double-stranded regions of RNAs generated by base pairing are stiffer than single-stranded regions. As a result, an RNA that has secondary structure will have a more rigid shape than one without double-stranded regions. Also, the intermingled paired regions cause the RNA to fold back on itself extensively, facilitating additional tertiary interactions. One type of tertiary interaction occurs when an unpaired region (such as the loop of a hairpin like that shown in Figure 2.2) pairs with another region of the same RNA molecule. A structure like this is called a pseudoknot (rather than a real knot) because it is held together only by hydrogen bonds. Together, these interactions give many RNAs a well-defined three-dimensional shape, called their tertiary structure. Proteins or other cellular constituents often recognize RNAs by their tertiary structures.