jackbauer! said:
you're being vague. there are many more than 4 proteins...
simple proteins (only amino acids), scleroproteins (structural), mucoproteins (bound to carbs), albumin/globulins (globular, enzymes), lipoproteins (bound to lipids) just to name a few.
Conjugated proteins(protein + nonprotein), nucleoproteins(protein wrapping the nucleic acid ex: histamine), metalloproteins(protein with metal ion), and chromoproteins(protein with pigment molecule).
That makes the 9 protein types.
As to protein structure
primary-AA(amino acid) sequence
secondary-folding
tertiary-more folding on top of the secondary
quaternary-two or more amino acid sequences interacting ex: hemoglobin