lon

Gene Description

lon (PP_2302) encodes the ATP-dependent Lon protease (also called protease La, EC 3.4.21.53), a soluble cytoplasmic enzyme of the peptidase S16 family. Lon is a self-compartmentalizing AAA+ protease that assembles into a homohexameric ring with a central cavity, coupling ATP binding and hydrolysis in its AAA+ module to the unfolding and processive translocation of substrate polypeptides into the proteolytic chamber, where a Ser-Lys catalytic dyad cleaves them into short peptides 5-10 residues long. It mediates the selective degradation of mutant, abnormal and misfolded proteins as well as certain short-lived regulatory proteins, contributing to protein quality control and cellular homeostasis. Lon is induced by heat shock and is important for survival under stress and DNA damage; it also binds double-stranded DNA in a site-specific manner.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0004176 ATP-dependent peptidase activity	IEA GO_REF:0000120	ACCEPT	Summary: Core molecular function. Lon is an ATP-dependent protease (protease La) whose AAA+ module couples ATP hydrolysis to substrate unfolding and processive proteolysis. Strongly supported by the peptidase S16 family assignment (UniProt SIMILARITY; MEROPS S16.001), the Lon InterPro signatures (IPR004815, IPR008269 Lon_proteolytic, IPR027065, IPR027543) and EC 3.4.21.53.
GO:0004252 serine-type endopeptidase activity	IEA GO_REF:0000120	ACCEPT	Summary: Accurate description of the catalytic mechanism. Lon is a serine endopeptidase that uses a Ser-Lys catalytic dyad (UniProt active sites Ser674 and Lys717) in its C-terminal proteolytic domain (Lon_proteolytic, IPR008269; PROSITE LON_PROTEOLYTIC). EC 3.4.21.53 is a serine protease activity. Accept as a supporting molecular function describing the proteolytic chemistry underlying GO:0004176.
GO:0005524 ATP binding	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: Correct supporting molecular function. Lon contains a P-loop AAA+ ATPase module (UniProt ATP-binding region 352-359; IPR003593 AAA+_ATPase, IPR003959 ATPase_AAA_core) that binds ATP. This is a more general term than the ATP hydrolysis activity (GO:0016887) also annotated; kept as non-core because both ATP binding and hydrolysis underpin the core ATP-dependent peptidase activity rather than being independent core functions.
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: Correct cellular component. Lon is a soluble cytoplasmic protease (UniProt SUBCELLULAR LOCATION Cytoplasm). Consistent with its role in degrading cytoplasmic regulatory and misfolded proteins.
GO:0006508 proteolysis	IEA GO_REF:0000002	KEEP AS NON CORE	Summary: Correct but general biological process. Lon degrades polypeptides processively into short peptides; proteolysis is the broad parent process. The more specific protein quality control and protein catabolic process terms below better capture the biological role, so this general term is kept as non-core.
GO:0006515 protein quality control for misfolded or incompletely synthesized proteins	IEA GO_REF:0000104	ACCEPT	Summary: Core biological process. Lon mediates the selective degradation of mutant, abnormal and misfolded proteins (UniProt FUNCTION), a central protein quality control activity. Accept as a core role of the gene.
GO:0016887 ATP hydrolysis activity	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: Correct supporting molecular function. The AAA+ module of Lon hydrolyzes ATP to drive substrate unfolding and translocation into the proteolytic chamber. This underpins the core ATP-dependent peptidase activity (GO:0004176); kept as non-core to avoid redundancy with that more specific term.
GO:0030163 protein catabolic process	IEA GO_REF:0000002	ACCEPT	Summary: Accurate biological process. Lon catabolizes proteins, degrading both abnormal proteins and short-lived regulatory proteins. Accept; this together with protein quality control captures the in vivo role.
GO:0034605 cellular response to heat	IEA GO_REF:0000104	KEEP AS NON CORE	Summary: Consistent with Lon biology. Lon is induced by heat shock (UniProt INDUCTION) and degrades the abnormal/misfolded proteins that accumulate under thermal stress, contributing to the heat-stress response. This is a downstream/contextual role rather than the core catalytic function; keep as non-core.
GO:0043565 sequence-specific DNA binding	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: Lon binds double-stranded DNA in a site-specific manner (UniProt FUNCTION), an activity reported for Lon homologs that may modulate its proteolytic activity. This is a secondary, non-catalytic property and not the core function of the protein; keep as non-core.

Gene Description

Existing Annotations Review

Core Functions

ATP-dependent serine protease (AAA+ peptidase) that couples ATP hydrolysis to processive unfolding and degradation of misfolded, abnormal and short-lived regulatory proteins, providing cytoplasmic protein quality control

References

Deep Research

Asta

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