Example sentences for: aaa

How can you use “aaa” in a sentence? Here are some example sentences to help you improve your vocabulary:

  • This basic domain organization shows a striking parallel to that of magnesium chelatase, a heterotrimeric enzyme containing BchD, BchI and BchH subunits, that performs ATP-dependent insertion of Mg 2+into the protoporphyrin IX ring in the course of chlorophyll biosynthesis [ 49 ] . In particular, the BchD subunit resembles midasin in possessing a single AAA protomer close to its NH 2 -terminus, together with a short aspartate-glutamate-rich region and a MIDAS-containing domain at its carboxy-terminus.

  • In both midasin and dynein, the evolutionary fusion of the six AAA protomers into a single polypeptide has permitted the individual protomers in the hexameric assembly to acquire substantial structural and functional specialization.

  • Concomitant with this development of asymmetrical structure, the AAA1 protomer of the dynein motor unit evolved a functional dominance, in which it alone retains the full ability for binding and hydrolysis of ATP, while AAA2, AAA3 and AAA4 have lost the capability for hydrolysis and the most degenerate protomers AAA5 and AAA6 show no significant binding of ATP [ 20 21 22 ] . In midasin, the specialization of AAA protomers appears to have taken a less drastic course than in dynein.

  • 1: GAT C TC GAT CCC GCG AAA TTA ATA CCA CTC ACT ATA GGG GAA TTG TGA GCG GAT AAC AAT TCC CCT (BglII site in bold)

  • One possibility is that the MIDAS site serves to attach protein ligands through a mechanism involving participation of a glutamate or aspartate residue on the ligand in the coordination of a Mg 2+ion at the MIDAS site of midasin, in a manner similar to that by which the MIDAS site in integrin I-domains appears to mediate attachment of collagen through the glutamate in the GFOGER binding motif [ 36 ] . Interestingly, the related RGE ligand-binding motif [ 41 ] occurs in a conserved region of the midasin AAA-domain (yeast, residues 1835-1838), as well as in the AAA-domain of Mg chelatases [ 32 ] . The presence of this consensus binding motif in the AAA domain raises the possibility of the midasin molecule folding back onto itself, with the M-domain becoming attached to one face of the AAA domain and perhaps regulating access to its central chamber, in a manner analogous to that in which the 19S proteasome regulator, also an AAA protein, controls access to the central proteolytic chamber of the proteasome [ 42 ] .


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