RNA

RNA is ribonucleic acid, a close cousin of deoxyribonucleic acid or DNA. RNA is a polymer of ribonucleoside-phosphates. It's backbone is comprised of alternating ribose and phosphate groups. Ribose is a five carbon sugar that is found in a puranose, or five-membered ring, form in RNA. The phosphate groups link consecutive ribose groups and each bear one negative charge. Each monomer also has a nitrogenous base for a side chain. The four commonly found side chains in RNA are adenine, cytosine, guanine and uracil. Several other bases are occasionaly found in RNAs including: thymine, pseudouridine and methylated cytosine and guanine.

Click on the links for 3D computer visualization of each molecule based on experimental data: RNA

Inside of cells, there are three major types of RNA: messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). There are a number of other types of RNA present in smaller quanitites as well, including small nuclear RNA (snRNA), small nucleolar RNA (snoRNA) and the 4.5S signal recognition particle (SRP) RNA. Novel species of RNA continue to be identified.

RNA serves a multitude of roles in living cells. These include: serving as a temporary copy of genes that is used as a template for protein synthesis (mRNA), functioning as adaptor molecules that decode the genetic code (tRNA) and catalyzing the synthesis of proteins (rRNA). There is much evidence implicating RNA structure in biological regulation and catalysis. Interestingly, RNA is the only biological polymer that serves as both a catalyst (like proteins) and as information storage (like DNA). For this reason, it has be postulated RNA, or an RNA-like molecule, was the basis of life early in evolution.

RNA is present in several forms - messenger RNA (mRNA), transfer RNA, and ribosomal RNA (rRNA). Each of these RNA forms is involved in different steps of protein synthesis. mRNA is generated from DNA and is the template for protein synthesis. tRNA is critical to the translation of the mRNA sequence into protein sequence. rRNA are components of the ribosomes which are the sites of protein synthesis.RNA is a polymer that contains ribose rather than deoxyribose sugars. The normal base composition is adenine, uracil, guanine, and cytosine.

RNA can form double stranded duplexes. These duplexes are in the A conformation because the 2'OH
precludes the B conformation.

More commonly, RNA is single stranded and can form complex and unusual shapes. One example is tRNA which contains about 70 bases that are folded such that there are base paired stems and open loops. The overall shape of the completely folded tRNA is L shaped.

Another very interesting type of RNA is called a ribozyme, which is an RNA that has catalytic activity.
Several ribozyme structures have been characterized.

Ribosomal subunits have been studied in great detail . The 30S ribosomal subunit and 50S ribosomal subunit consists of rRNA and multiple proteins.

Web Author: Tug Sezen