5.

A classification of non-permanent membrane proteins (modified from [160])

Type	Examples	References
(A) According to the reversibility of the membrane contact
(1) Proteins that interact reversibly with the membrane	Lipid transfer proteins Ceramide-activated protein kinase	[168, 179, 181]
(2) Proteins with very long-lived (irreversible) contacts	Bacterial toxins (e.g. aerolysin) Blood coagulation factors.	[187, 197]
(B) According to the nature (strength) of the interaction
(1) Proteins that interact weakly with the membrane (extrinsic-like)	TrwD Protein kinases C	[176]
(2) Proteins that interact strongly with the membrane:
(2.1) Without covalent modification of the lipid (intrinsic like)	RTX toxins Complement proteins	[196]
(2.2) With covalent modification of the lipid	Phospholipases Enzymes of lipid metabolism	[182]