TY  - JOUR
AU  - Braun, Tatjana
AU  - Orlova, Albina
AU  - Valegård, Karin
AU  - Lindås, Ann-Christin
AU  - Schröder, Gunnar
AU  - Egelman, Edward H.
TI  - Archaeal actin from a hyperthermophile forms a single-stranded filament
JO  - Proceedings of the National Academy of Sciences of the United States of America
VL  - 112
IS  - 30
SN  - 1091-6490
CY  - Washington, DC
PB  - National Acad. of Sciences
M1  - FZJ-2015-05066
SP  - 9340 - 9345
PY  - 2015
AB  - The prokaryotic origins of the actin cytoskeleton have been firmly established, but it has become clear that the bacterial actins form a wide variety of different filaments, different both from each other and from eukaryotic F-actin. We have used electron cryomicroscopy (cryo-EM) to examine the filaments formed by the protein crenactin (a crenarchaeal actin) from Pyrobaculum calidifontis, an organism that grows optimally at 90 °C. Although this protein only has ∼20% sequence identity with eukaryotic actin, phylogenetic analyses have placed it much closer to eukaryotic actin than any of the bacterial homologs. It has been assumed that the crenactin filament is double-stranded, like F-actin, in part because it would be hard to imagine how a single-stranded filament would be stable at such high temperatures. We show that not only is the crenactin filament single-stranded, but that it is remarkably similar to each of the two strands in F-actin. A large insertion in the crenactin sequence would prevent the formation of an F-actin-like double-stranded filament. Further, analysis of two existing crystal structures reveals six different subunit-subunit interfaces that are filament-like, but each is different from the others in terms of significant rotations. This variability in the subunit-subunit interface, seen at atomic resolution in crystals, can explain the large variability in the crenactin filaments observed by cryo-EM and helps to explain the variability in twist that has been observed for eukaryotic actin filaments.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000358656500063
C6  - pmid:26124094
DO  - DOI:10.1073/pnas.1509069112
UR  - https://juser.fz-juelich.de/record/202943
ER  -