Several peripheral membrane proteins are known to form
membrane
pores through multimerization. In many cases, in biochemical reconstitution
experiments, a complex distribution of oligomeric states has been
observed that may, in part, be irrelevant to their physiological functions.
This phenomenon makes it difficult to identify the functional oligomeric
states of membrane lipid interacting proteins, for example, during
the formation of transient membrane pores. Using fibroblast growth
factor 2 (FGF2) as an example, we present a methodology applicable
to giant lipid vesicles by which functional oligomers can be distinguished
from nonspecifically aggregated proteins without functionality. Two
distinct populations of fibroblast growth factor 2 were identified
with (i) dimers to hexamers and (ii) a broad population of higher
oligomeric states of membrane-associated FGF2 oligomers significantly
distorting the original unfiltered histogram of all detectable oligomeric
species of FGF2. The presented statistical approach is relevant for
various techniques for characterizing membrane-dependent protein oligomerization.