Purity > 90% as determined by SDS-PAGE. MW: 67.7kDa. Full Length of Mature Protein: 2-487aa. N-terminal 6xHis-SUMO-tagged. Enterobacteria phage T4 (Bacteriophage T4). Chaperone responsible for attachment of long tail fibers to virus particle. During phage assembly, twelve fibritin molecules attach to the phage neck via gp13: six molecules forming the collar and six molecules forming the whiskers.