Ca 2+ -loaded spherulin 3a from Physarum polycephalum adopts the prototype γ-crystallin fold in aqueous solution 1 1Edited by P. E. Wright

Autor: Christian Renner, Tad A. Holak, Rainer Jaenicke, Eva-Maria Mayr, Burkhard Rosinke
Rok vydání: 1997
Předmět:
Zdroj: Journal of Molecular Biology. 271:645-655
ISSN: 0022-2836
DOI: 10.1006/jmbi.1997.1184
Popis: Spherulin 3a is the most abundantly expressed cytosolic protein in spherulating plasmodia of the slime mold Physarum polycephalum. High yields of unlabeled, uniformly 15N and uniformly 13C/15N-labeled recombinant spherulin 3a from Escherichia coli could be produced by a simple protocol described here. The three-dimensional solution structure of Ca2+-loaded spherulin 3a was determined by homo- and heteronuclear NMR spectroscopy. The structure of monomeric spherulin 3a consists of two pleated β-sheets plus a short α-helix arranged into the γ-crystallin fold. The β-sheets comprise two intertwined Greek-key motifs. An additional N-terminal β-strand is unique to spherulin 3a. Complexation of calcium ions greatly enhances overall conformational stability of the protein. The average atomic root-mean-square deviations (r.m.s.d.) for heavy atoms in β-strands were 0.34(±0.16) A for the backbone atoms and 0.73(±0.40) A for all atoms. The corresponding r.m.s.d. values for heavy atoms in the whole protein were 0.62(±0.42) A for the backbone atoms and 0.99(±0.65) A for all atoms. We show the structural relationship between spherulin 3a, a myxomycete dormancy protein, and crystallins from the vertebrate eye lens. Since spherulin 3a has a structure corresponding to one domain of bovine γB(II)-crystallin, it represents a hypothetical ancestral γ-crystallin precursor structure.
Databáze: OpenAIRE
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