Structures of actin-bound Wiskott-Aldrich syndrome protein homology 2 (WH2) domains of Spire and the implication for filament nucleation.
Three classes of proteins are known to nucleate new filaments: the Arp2/3 complex, formins, and the third group of proteins that contain ca. 25 amino acid long actin-binding Wiskott-Aldrich syndrome protein homology 2 domains, called the WH2 repeats. Crystal structures of the complexes between the actin-binding WH2 repeats of the Spire protein and actin were determined for the Spire single WH2 domain D, the double (SpirCD), triple (SpirBCD), quadruple (SpirABCD) domains, and an artificial Spire WH2 construct comprising three identical D repeats (SpirDDD). SpirCD represents the minimal functional core of Spire that can nucleate actin filaments. Packing in the crystals of the actin complexes with SpirCD, SpirBCD, SpirABCD, and SpirDDD shows the presence of two types of assemblies, "side-to-side" and "straight-longitudinal," which can serve as actin filament nuclei. The principal feature of these structures is their loose, open conformations, in which the sides of actins that normally constitute the inner interface core of a filament are flipped inside out. These Spire structures are distant from those seen in the filamentous nuclei of Arp2/3, formins, and in the F-actin filament.
Max-Planck-Institut für Biochemie, 82152 Martinsried, Germany.
Anna M
AM
Ducka
Peteranne
P
Joel
Grzegorz M
GM
Popowicz
Kathleen M
KM
Trybus
Michael
M
Schleicher
Angelika A
AA
Noegel
Robert
R
Huber
Tad A
TA
Holak
Tomasz
T
Sitar
D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D040681:Structural Homology, Protein; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D000199:Actins; D029721:Drosophila Proteins; D008840:Microfilament Proteins; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; D051300:Wiskott-Aldrich Syndrome Protein Family; C402385:spir protein, Drosophila