简介：Thecodontableforthecanonicalgeneticcodecanberearrangedinsuchawaythatthecodeisdividedintofourquartersandtwohalvesaccordingtothevari-abilityoftheirGCandpurinecontents,respectively.Forprokaryoticgenomes,whenthegenomicGCcontentincreases,theiraminoacidcontentstendtoberestrictedtotheGC-richquarterandthepurine-contentinsensitivehalf,whereallcodonsarefourfolddegenerateandrelativelymutation-tolerant.Conversely,whenthegenomicGCcontentdecreases,mostofthecodonsretracttotheAU-richquarterandthepurine-contentsensitivehalf;mostofthecodonsnotonlyremainencodingphysicochemicallydiversifiedaminoacidsbutalsovarywhentransversion(betweenpurineandpyrimidine)happens.Aminoacidswithsixfold-degeneratecodonsaredistributedintoallfourquartersandacrossthetwohalves;theirfourfold-degeneratecodonsareallpartitionedintothepurine-insensitivehalfinfavoriteofrobustnessagainstmutations.Thefeaturesmanifestedinthere-arrangedcodontableexplainmostoftheintrinsicrelationshipbetweenproteincodingsequences(theinformationalcontent)andaminoacidcompositions(thefunctionalcontent).Therenovatedcodontableisusefulinpredictingabundantaminoacidsandpositioningtheaminoacidswithrelatedordistinctphysicochem-icalproperties.