Structure
The 3-D structure of RNase H commonly consists of a 5-stranded β-sheet surrounded by a distribution of α-helices. In some RNase H, such as the one found in HIV-1, the enzyme is missing one of the helices known as the C-helix, a positively charged α-helix whose protrusive shape increases substrate binding capacity. The active site of the enzyme is centered around a conserved DEDD motif (composed of residues: D443, E478, D498, and D549) which performs the hydrolysis of the RNA substrate. A magnesium ion is commonly used as a cofactor during the hydrolysis step. It is also a potential but unconfirmed mechanism in which multiple ions are necessary for to perform the hydrolysis. The enzyme also contains a nucleic acid binding cleft about 60 Å in length that can encompass a region of 18 bound RNA/DNA base pairs.
Read more about this topic: RNase H
Famous quotes containing the word structure:
“Who says that fictions only and false hair
Become a verse? Is there in truth no beauty?
Is all good structure in a winding stair?
May no lines pass, except they do their duty
Not to a true, but painted chair?”
—George Herbert (1593–1633)
“There is no such thing as a language, not if a language is anything like what many philosophers and linguists have supposed. There is therefore no such thing to be learned, mastered, or born with. We must give up the idea of a clearly defined shared structure which language-users acquire and then apply to cases.”
—Donald Davidson (b. 1917)
“A structure becomes architectural, and not sculptural, when its elements no longer have their justification in nature.”
—Guillaume Apollinaire (1880–1918)