Structure of the ribosome associating GTPase HflX.
The HflX-family is a widely distributed but poorly characterized family of translation factor-related guanosine triphosphatases (GTPases) that interact with the large ribosomal subunit. This study describes the crystal structure of HflX from Sulfolobus solfataricus solved to 2.0-A resolution in apo- and GDP-bound forms. The enzyme displays a two-domain architecture with a novel "HflX domain" at the N-terminus, and a classical G-domain at the C-terminus. The HflX domain is composed of a four-stranded parallel beta-sheet flanked by two alpha-helices on either side, and an anti-parallel coiled coil of two long alpha-helices that lead to the G-domain. The cleft between the two domains accommodates the nucleotide binding site as well as the switch II region, which mediates interactions between the two domains. Conformational changes of the switch regions are therefore anticipated to reposition the HflX-domain upon GTP-binding. Slow GTPase activity has been confirmed, with an HflX domain deletion mutant exhibiting a 24-fold enhanced turnover rate, suggesting a regulatory role for the HflX domain. The conserved positively charged surface patches of the HflX-domain may mediate interaction with the large ribosomal subunit. The present study provides a structural basis to uncover the functional role of this GTPases family whose function is largely unknown.
Wu
Hao
H
Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands.
Sun
Lei
L
Blombach
Fabian
F
Brouns
Stan J J
SJ
Snijders
Ambrosius P L
AP
Lorenzen
Kristina
K
van den Heuvel
Robert H H
RH
Heck
Albert J R
AJ
Fu
Sheng
S
Li
Xuemei
X
Zhang
Xuejun C
XC
Rao
Zihe
Z
van der Oost
John
J
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019204:GTP-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D055672:Static Electricity; D048229:Sulfolobus solfataricus / Q000201:enzymology* / Q000235:genetics
D019843:Archaeal Proteins; D011994:Recombinant Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins