A further look at the logic and enzymatic machinery of proteome posttranslational modifications turns up additional noncanonical examples of phosphorus chemical biology. Four such examples include (1) dehydroalanyl and lanthionyl residues in thousands of microbial proteins that arise via enzymatic formation and processing of P-Ser-protein intermediates. (2) Tyrosyl-AMP modifications are congeners of Tyr–OPO₃²⁻ logic. (3) Phosphocholine addition to certain serine side chains generates protein-Ser–O–P choline phosphodiester links. (4) Finally, in the course of assembly of apoptosomes in cells the small ubiquitin-like protein autophagy related protein 8 (Agt8) engages in covalent phosphodiester linkage to the membrane phospholipid phosphatidylcholine, an unusual protein lipidation strategy for a specific purpose.