Staphylococcus aureus genome analyses revealed the presence of a giant gene 31494 bp in length. The putative protein of ca. 1.1 MDa encoded by this gene shows homology to the major adhesion protein of Streptococcus defectivus, Emb, a protein that binds to the extracellular matrix (ECM) of host cells, and therefore the giant protein was named Ebh (ECM binding protein homologue). Ebh consists of several distinct regions, including a large central region with 52 imperfect repeats of 126 amino acid residues. In the present study, we investigated the structure of this giant molecule by X-ray crystallography, CD spectrometry, and small-angle X-ray scattering (SAXS). The crystal structure of two repeats showed that each repeat consists of two distinct three-helix bundles, and two such repeats are connected along the long axis resulting in a 120 Å rod-like structure. CD and SAXS analyses of the samples with longer repeats suggested that each repeat has an identical structure and such repeats are connected tandemly to form a rod-like structure in solution the length of which increased proportionately to the number of repeating units. On the basis of these results, it was proposed that Ebh is a 320nm rod-like molecule with some plasticity at module junctions.