A BIOCHEMICAL-CHARACTERIZATION OF THE PHOTOPHORE LENSES OF THE MIDSHIPMAN FISH, PORICHTHYS-NOTATUS GIRARD

The present study is a biochemical characterization of the photophore lenses of the midshipman fish, Porichthys notatus, a species that bear s 800 photophores cal properties of the photophore lenses were compare d with those of the eye lens with which they share a similar developme ntal origin and analogous function. To achieve a high refractive index , the vertebrate eye lens has a relatively high concentration of struc tural proteins (20-50%, depending on species) and a simple protein com position, that is, relatively few proteins are synthesized in comparis on to other tissues. Similarly, the photophore lenses of P. notatus ha d a relatively high protein concentration (average=29%, n=5) and appro ximately 60% of the total soluble protein was represented by two subun it species of 33 kD and 35 kD on denaturing polyacrylamide gels. The s tructural proteins of the eye lens are of two principle types: 1) beta and gamma polypeptides which belong to vertebrate lens-specific cryst allin families, and, 2) enzymes recruited into the lens which take on the function of structural proteins. Here, we report that the two majo r photophore lens subunits of 33 kD and 35 kD are biochemically simila r to each other, but are clearly distinct from any of the previously c haracterized crystallins. Therefore, we propose that photophore lenses appear to recruit a novel protein.