Involved in the biosynthesis of the peptidolactone antibiotic etamycin (viridogrisein) (PubMed:6324794, PubMed:8546682). Catalyzes the hydroxylation of free L-proline at the C-4 position to yield trans-4-hydroxy-L-proline (PubMed:6324794, PubMed:8546682). 2-oxoglutarate + L-proline + O2 = CO2 + succinate + trans-4-hydroxy-L-proline Binds 1 Fe(2+) ion. Competitively inhibited by pyridine-2,4-dicarboxylate (PubMed:8546682). Inhibited by diethyl pyrocarbonate (DEPC), 3,4-dihydroxybenzoate, pyridine-2,5-dicarboxylate, alpha,alpha'-dipyridyl, and some metal ions such as Co(2+) and Zn(2+) (PubMed:6324794, PubMed:8546682). Optimum pH is 7.5. Optimum temperature is 25 degrees Celsius. Antibiotic biosynthesis. Monomer. Belongs to the PhyH family.