Scientific Reports (Mar 2021)

The less conserved metal-binding site in human CRISP1 remains sensitive to zinc ions to permit protein oligomerization

  • Jie Sheng,
  • Bart M. Gadella,
  • Nick K. Olrichs,
  • Dora V. Kaloyanova,
  • J. Bernd Helms

DOI
https://doi.org/10.1038/s41598-021-84926-y
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 10

Abstract

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Abstract Cysteine-rich secretory proteins (CRISPs) are a subgroup of the CRISP, antigen 5 and PR-1 (CAP) superfamily that is characterized by the presence of a conserved CAP domain. Two conserved histidines in the CAP domain are proposed to function as a Zn2+-binding site with unknown function. Human CRISP1 is, however, one of the few family members that lack one of these characteristic histidine residues. The Zn2+-dependent oligomerization properties of human CRISP1 were investigated using a maltose-binding protein (MBP)-tagging approach in combination with low expression levels in XL-1 Blue bacteria. Moderate yields of soluble recombinant MBP-tagged human CRISP1 (MBP-CRISP1) and the MBP-tagged CAP domain of CRISP1 (MBP-CRISP1ΔC) were obtained. Zn2+ specifically induced oligomerization of both MBP-CRISP1 and MBP-CRISP1ΔC in vitro. The conserved His142 in the CAP domain was essential for this Zn2+ dependent oligomerization process, confirming a role of the CAP metal-binding site in the interaction with Zn2+. Furthermore, MBP-CRISP1 and MBP-CRISP1ΔC oligomers dissociated into monomers upon Zn2+ removal by EDTA. Condensation of proteins is characteristic for maturing sperm in the epididymis and this process was previously found to be Zn2+-dependent. The Zn2+-induced oligomerization of human recombinant CRISP1 may shed novel insights into the formation of functional protein complexes involved in mammalian fertilization.