1am2: Difference between revisions

[[Image:1am2.gif|left|200px]]<br /><applet load="1am2" size="350" color="white" frame="true" align="right" spinBox="true"  

Several genes from prokaryotes and lower eukaryotes have been found to contain an in-frame open reading frame, which encodes for an internal protein (intein). Post-translationally, the internal polypeptide auto-splices and ligates the external sequences to yield a functional external protein (extein) and an intein. Most, but not all inteins, contain, apart from a splicing domain, a separate endonucleolytic domain that enables them to maintain their presence by a homing mechanism. We report here the crystal structure of an intein found in the gyrase A subunit from Mycobacterium xenopi at 2.2 A resolution. The structure contains an unusual beta-fold with the catalytic splice junctions at the ends of two adjacent antiparallel beta-strands. The arrangement of the active site residues Ser 1, Thr 72, His 75, His 197, and Asn 198 is consistent with a four-step mechanism for the cleavage-ligation reaction. Using site-directed mutagenesis, the N-terminal cysteine, proposed as the nucleophile in the first step of the splicing reaction, was changed to a Ser 1 and Ala 0, thus capturing the intein in a pre-spliced state.

1AM2 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mycobacterium_xenopi Mycobacterium xenopi]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AM2 OCA].  

[[Category: Sacchettini, J C.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:45:58 2008''