Objectives To overcome the limited production capability of shell matrix proteins and efficiently conduct in vitro CaCO3 biomineralization studies, a putative recombinant shell matrix protein was prepared and characterized. Results A glycine-rich protein (GRP_BA) was found in Pinctada fucata as a putative shell matrix protein (NCBI reference sequence; BAA20465). It was genetically redesigned for the production in Escherichia coli. The recombinant protein was obtained in a 400 ml shake-flask culture at approx. 30 mg l(-1) with a purity of > 95 %. It efficiently formed a complex with Ca2+. Ca2+-induced agglomeration was like other calcification-related proteins. Spherulitic calcite micro-particles, 20-30 A mu m diam. with rosette- and sphere-like structures were synthesized in the presence of the recombinant shell protein, which could be formed by stacking and/or aggregation of calcite nanograins and the bound protein. Conclusions Recombinant production of a shell matrix protein could overcome potential difficulties associated with the limited amount of protein available for biomineralization studies and provide opportunities to fabricate biominerals in practical aspects.