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@ARTICLE{Bustad:601545,
author = {Bustad, Helene J. and Christie, Marthe S. and Laitaoja,
Mikko and Aarsand, Aasne K. and Martinez, Aurora and Jänis,
Janne and Kallio, Juha P.},
title = {{O}ne ring closer to a closure: the crystal structure of
the {ES}$_3$ hydroxymethylbilane synthase intermediate},
journal = {The FEBS journal},
volume = {291},
number = {3},
issn = {0014-2956},
address = {Oxford [u.a.]},
publisher = {Wiley-Blackwell},
reportid = {PUBDB-2024-00254},
pages = {510 - 526},
year = {2023},
note = {online first},
abstract = {Hydroxymethylbilane synthase (HMBS), involved in haem
biosynthesis, catalyses the head-to-tail coupling of four
porphobilinogens (PBGs) via a dipyrromethane (DPM) cofactor.
DPM is composed of two PBGs, and a hexapyrrole is built
before the tetrapyrrolic 1-hydroxymethylbilane product is
released. During this elongation, stable enzyme (E)
intermediates are formed from the holoenzyme, with
additional PBG substrates (S): ES, ES$_2$, ES$_3$ and
ES$_4$. Native PAGE and mass spectrometry of the acute
intermittent porphyria (AIP)-associated HMBS variant
p.Arg167Gln demonstrated an increased amount of ES$_3$.
Kinetic parameters indicated catalytic dysfunction, however,
the product release was not entirely prevented. Isolation
and crystal structure analysis of the ES$_3$ intermediate
(PDB: 8PND) showed that a pentapyrrole was fully retained
within the active site, revealing that polypyrrole
elongation proceeds within the active site via a third
interaction site, intermediate pyrrole site 3 (IPS3). The
AIP-associated HMBS variant p.Arg195Cys, located on the
opposite side to p.Arg167Gln in the active site, accumulated
the ES$_4$ intermediate in the presence of excess PBG,
implying that product hydrolysis was obstructed. Arg167 is
thus involved in all elongation steps and is a determinant
for the rate of enzyme catalysis, whereas Arg195 is
important for releasing the product. Moreover, by
substituting residues in the vicinity of IPS3, our results
indicate that a fully retained hexapyrrole could be
hydrolysed in a novel site in proximity of the IPS3.},
cin = {DOOR ; HAS-User},
ddc = {610},
cid = {I:(DE-H253)HAS-User-20120731},
pnm = {6G3 - PETRA III (DESY) (POF4-6G3)},
pid = {G:(DE-HGF)POF4-6G3},
experiment = {EXP:(DE-H253)P-P11-20150101},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:37863644},
UT = {WOS:001096057200001},
doi = {10.1111/febs.16982},
url = {https://bib-pubdb1.desy.de/record/601545},
}