The vertex of y2=x is at (0,0), which is not on the curve y=ex, so we need an exponential function which passes through (0,0). y=ex-1 is such an exponential function. If the vertex moves to a point (h,k) where k=eh-1, then the equation of the parabola changes to (y-k)2=x-h, that is, (y-eh+1)2=x-h. For example, when h=1, the equation becomes (y-e+1)2=x-1.
Below is a representation of the series of parabolas created by using the exponential trajectory of the vertex.

The red curve is y=ex-1 and the series of parabolas is shown in blue.