3CS1

Flagellar Calcium-binding Protein (FCaBP) from T. cruzi

Summary for 3CS1

• Entry DOI: 10.2210/pdb3cs1/pdb
• Descriptor: Flagellar calcium-binding protein (2 entities in total)
• Functional Keywords: flagella, calcium-binding, myristoylated, palmitoylated, sensor, membrane targeting, ef-hand, cell projection, cilium, flagellum, metal binding protein
• Biological source: Trypanosoma cruzi
• Cellular location: Cell projection, cilium, flagellum: P07749
• Total number of polymer chains: 1
• Total formula weight: 24955.06

Authors

Ames, J.B.,Ladner, J.E.,Wingard, J.N.,Robinson, H.,Fisher, A. (deposition date: 2008-04-08, release date: 2008-06-24, Last modification date: 2025-03-26)

Primary citation

Wingard, J.N.,Ladner, J.,Vanarotti, M.,Fisher, A.J.,Robinson, H.,Buchanan, K.T.,Engman, D.M.,Ames, J.B.
Structural Insights into Membrane Targeting by the Flagellar Calcium-binding Protein (FCaBP), a Myristoylated and Palmitoylated Calcium Sensor in Trypanosoma cruzi.
J.Biol.Chem., 283:23388-23396, 2008

PubMed Abstract: The flagellar calcium-binding protein (FCaBP) of the protozoan Trypanosoma cruzi is targeted to the flagellar membrane where it regulates flagellar function and assembly. As a first step toward understanding the Ca(2+)-induced conformational changes important for membrane-targeting, we report here the x-ray crystal structure of FCaBP in the Ca(2+)-free state determined at 2.2A resolution. The first 17 residues from the N terminus appear unstructured and solvent-exposed. Residues implicated in membrane targeting (Lys-19, Lys-22, and Lys-25) are flanked by an exposed N-terminal helix (residues 26-37), forming a patch of positive charge on the protein surface that may interact electrostatically with flagellar membrane targets. The four EF-hands in FCaBP each adopt a "closed conformation" similar to that seen in Ca(2+)-free calmodulin. The overall fold of FCaBP is closest to that of grancalcin and other members of the penta EF-hand superfamily. Unlike the dimeric penta EF-hand proteins, FCaBP lacks a fifth EF-hand and is monomeric. The unstructured N-terminal region of FCaBP suggests that its covalently attached myristoyl group at the N terminus may be solvent-exposed, in contrast to the highly sequestered myristoyl group seen in recoverin and GCAP1. NMR analysis demonstrates that the myristoyl group attached to FCaBP is indeed solvent-exposed in both the Ca(2+)-free and Ca(2+)-bound states, and myristoylation has no effect on protein structure and folding stability. We propose that exposed acyl groups at the N terminus may anchor FCaBP to the flagellar membrane and that Ca(2+)-induced conformational changes may control its binding to membrane-bound protein targets.

PubMed: 18559337
DOI: 10.1074/jbc.M803178200

Experimental method

X-RAY DIFFRACTION (2 Å)