Structure and function of an atypical homodimeric actin capping protein from the malaria parasite

DOI: 10.1007/s00018-021-04032-0

Authors: Abris Adam Bendes (University of Oulu) , Petri Kursula (University of Oulu; University of Bergen) , Inari Kursula (University of Oulu; University of Bergen)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Cellular And Molecular Life Sciences , VOL 79

State: Published (Approved)
Published: February 2022

Abstract: Apicomplexan parasites, such as Plasmodium spp., rely on an unusual actomyosin motor, termed glideosome, for motility and host cell invasion. The actin filaments are maintained by a small set of essential regulators, which provide control over actin dynamics in the different stages of the parasite life cycle. Actin filament capping proteins (CPs) are indispensable heterodimeric regulators of actin dynamics. CPs have been extensively characterized in higher eukaryotes, but their role and functional mechanism in Apicomplexa remain enigmatic. Here, we present the first crystal structure of a homodimeric CP from the malaria parasite and compare the homo- and heterodimeric CP structures in detail. Despite retaining several characteristics of a canonical CP, the homodimeric Plasmodium berghei (Pb)CP exhibits crucial differences to the canonical heterodimers. Both homo- and heterodimeric PbCPs regulate actin dynamics in an atypical manner, facilitating rapid turnover of parasite actin, without affecting its critical concentration. Homo- and heterodimeric PbCPs show partially redundant activities, possibly to rescue actin filament capping in life cycle stages where the β-subunit is downregulated. Our data suggest that the homodimeric PbCP also influences actin kinetics by recruiting lateral actin dimers. This unusual function could arise from the absence of a β-subunit, as the asymmetric PbCP homodimer lacks structural elements essential for canonical barbed end interactions suggesting a novel CP binding mode. These findings will facilitate further studies aimed at elucidating the precise actin filament capping mechanism in Plasmodium.

Journal Keywords: Actin-binding protein; Actin polymerization; Gliding motility; Polymerization kinetics; Regulation; Small-angle X-ray scattering; X-ray crystallography

Diamond Keywords: Malaria

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: B21-High Throughput SAXS , I04-1-Macromolecular Crystallography (fixed wavelength)

Added On: 16/02/2022 09:17

Discipline Tags:

Pathogens Infectious Diseases Disease in the Developing World Health & Wellbeing Biochemistry Chemistry Structural biology Life Sciences & Biotech Parasitology

Technical Tags:

Diffraction Scattering Macromolecular Crystallography (MX) Small Angle X-ray Scattering (SAXS)