In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 19 ( 2016-05-10), p. 5257-5262
Abstract:
Carbonic anhydrases are mostly zinc metalloenzymes that catalyze the reversible hydration/dehydration of CO 2 /HCO 3 − . Previously, the X-ray crystal structures of CO 2 -bound holo (zinc-bound) and apo (zinc-free) human carbonic anhydrase IIs (hCA IIs) were captured at high resolution. Here, we present sequential timeframe structures of holo- [ T = 0 s (CO 2 -bound), 50 s, 3 min, 10 min, 25 min, and 1 h] and apo-hCA IIs [ T = 0 s, 50 s, 3 min, and 10 min] during the “slow” release of CO 2 . Two active site waters, W DW (deep water) and W DW ′ (this study), replace the vacated space created on CO 2 release, and another water, W I (intermediate water), is seen to translocate to the proton wire position W1. In addition, on the rim of the active site pocket, a water W2′ (this study), in close proximity to residue His64 and W2, gradually exits the active site, whereas His64 concurrently rotates from pointing away (“out”) to pointing toward (“in”) active site rotameric conformation. This study provides for the first time, to our knowledge, structural “snapshots” of hCA II intermediate states during the formation of the His64-mediated proton wire that is induced as CO 2 is released. Comparison of the holo- and apo-hCA II structures shows that the solvent network rearrangements require the presence of the zinc ion.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1520786113
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2016
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
