  The Anderson metal-insulator transition is a fundamental phenomenon in
condensed matter physics, describing the transition from a conducting
(metallic) to a non-conducting (insulating) state driven by disorder in a
material. At the critical point of the Anderson transition, wave functions
exhibit multifractal behavior, and energy levels display a universal
distribution, indicating non-trivial correlations in the eigenstates. Recent
studies have shown that proteins, traditionally considered as insulators,
exhibit much higher conductivity than previously assumed. In this paper, we
investigate several proteins known for their efficient electron transport
properties. We compare their energy level statistics, eigenfunction
correlation, and electron return probability to those expected in metallic,
insulating, or critical states. Remarkably, these proteins exhibit properties
of critically disordered metals in their natural state without any parameter
adjustment. Their composition and geometry are self-organized into the critical
state of the Anderson transition, and their fractal properties are universal
and unique among critical systems. Our findings suggest that proteins' wave
functions fulfill "holographic" area laws, and the correlation fractal
dimension is precisely $d_2=2$.
