Sandbox Reserved 1644: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 77: | Line 77: | ||
<p align="justify">The '''active site''' represent by 2x36 is composed of''' six [https://en.wikipedia.org/wiki/Protomer protomers]''' in the asymmetric unite. One protomer counts nine [https://en.wikipedia.org/wiki/Beta_sheet b-strands] and seven [https://en.wikipedia.org/wiki/Alpha_helix a-helices]. An analysis of the complex’ structure suggested that '''two pair of protomers''' form A:B and C:D dimers and that the '''two''' remaining ones remain '''uncoupled'''. The dimer interface A:B/C:D is mostly linked by one another through '''hydrophilic interactions''', where the a1-helix is packed against the b3-strand and the loop between b7 and b8 makes inter-subunit contacts with b2<ref>PMID: 20222013</ref>. | <p align="justify">The '''active site''' represent by 2x36 is composed of''' six [https://en.wikipedia.org/wiki/Protomer protomers]''' in the asymmetric unite. One protomer counts nine [https://en.wikipedia.org/wiki/Beta_sheet b-strands] and seven [https://en.wikipedia.org/wiki/Alpha_helix a-helices]. An analysis of the complex’ structure suggested that '''two pair of protomers''' form A:B and C:D dimers and that the '''two''' remaining ones remain '''uncoupled'''. The dimer interface A:B/C:D is mostly linked by one another through '''hydrophilic interactions''', where the a1-helix is packed against the b3-strand and the loop between b7 and b8 makes inter-subunit contacts with b2<ref>PMID: 20222013</ref>. | ||
As all LonA proteins, ''h''Lon catalytic activity relies on a '''Ser-Lys dyad'''. Ser855 on a2 conducts the catalytic cleavage with the assistance of Lys898 on a3 through their [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen-bonding]. The lysine works as a general [https://en.wikipedia.org/wiki/Base_(chemistry) base] which, in | As all LonA proteins, ''h''Lon catalytic activity relies on a '''Ser-Lys dyad'''. Ser855 on a2 conducts the catalytic cleavage with the assistance of Lys898 on a3 through their [https://en.wikipedia.org/wiki/Hydrogen_bond hydrogen-bonding]. The lysine works as a general [https://en.wikipedia.org/wiki/Base_(chemistry) base] along with Thr880 which, in their deprotonated form, abstract the proton from the [https://en.wikipedia.org/wiki/Nucleophile nucleophilic] serine. Those three residues constitute the catalytic core. A characteristic of ''h''LonP is that the [https://en.wikipedia.org/wiki/310_helix 3(10)] helix at the N-terminal end of a2 is able to bring an '''additional residue into the active site''', Asp852. This most likely enables Lys898 [https://en.wikipedia.org/wiki/Acid_dissociation_constant pKa] lowering by creating a [https://en.wikipedia.org/wiki/Hydrophobe hydrophobic] environment, and thus, prevents the dyad to cut off protein substrates. This catalytic '''inactive form''' is also supported by the Asp852 and Trp770 residues that contribute to the catalytic site obstruction. Asp852 removal from the active site through conformational changes enables ''h''Lon to reach an open state that can hydrolyze protein substrate through ATP consumption<ref>PMID: 20222013</ref>.</p> | ||
