  Among all the proteins of Periplasmic C type cytochrome A (PPCA) family
obtained from cytochrome C7 found in Geobacter sulfurreducens, PPCA protein can
interact with Deoxycholate (DXCA), while its other homologs do not, as observed
from the crystal structures. Utilizing the concept of 'structure-function
relationship', an effort has been initiated towards understanding the driving
force for recognition of DXCA exclusively by PPCA among its homologs. Further,
a combinatorial analysis of the binding sequences (contiguous sequence of amino
acid residues of binding locations) is performed to build graph-theoretic
models, which show that PPCA differs from its homologues. Analysis of the
results suggests that the underlying impetus of recognition of DXCA by PPCA is
embedded in its primary sequence and 3D conformation.
