  The Protein Data Bank (PDB) today contains more than 153,000 entries with the
3-dimensional structures of biological macromolecules. Using the rich resources
of this repository, it is possible identifying subsets with specific,
interesting properties for different applications. Our research group prepared
an automatically updated list of amyloid- and probably amyloidogenic molecules,
the PDB\_Amyloid collection, which is freely available at the address
\url{http://pitgroup.org/amyloid}. This resource applies exclusively the
geometric properties of the steric structures for identifying amyloids. In the
present contribution, we analyze the starting (i.e., prefix) subsequences of
the characteristic, parallel beta-sheets of the structures in the PDB\_Amyloid
collection, and identify further appearances of these length-5 prefix
subsequences in the whole PDB data set. We have identified this way numerous
proteins, whose normal or irregular functions involve amyloid formation,
structural misfolding, or anti-coagulant properties, simply by containing these
prefixes: including the T-cell receptor (TCR), bound with the major
histocompatibility complexes MHC-1 and MHC-2; the p53 tumor suppressor protein;
a mycobacterial RNA polymerase transcription initialization complex; the human
bridging integrator protein BIN-1; and the tick anti-coagulant peptide TAP.
