The annotation of genomes sometimes describes the presence of tail lysins (in the present case Bacillus phage has a putative tail lysin 2). What is the difference between endolysin and tail lysin? What is the function of tail lysins?
I could certainly be wrong in this, but I believe endolysins are those lysins expressed at the time of cell lysis while tail lysins are those required for cell infection. Endolysins work together with holins. This review (http://www.sciencedirect.com/science/article/pii/S0924857907002038) discusses endolysins but doesn't mention tail lysins at all, unfortunately.
The issue seems to be clouded further by how databases like Uniprot have some very similar phage proteins annotated as "tail lysin" and "phage lysin" interchangeably.
Harry is right about endolysins. Usually, a phage lysis module is composed of endolysin and a holin. The latter is a small hydrophobic protein that eventually creates holes in the bacterial membrane. Endolysin passes through those holes and digest bacterial peptidoglycan witch ultimately results in cell lysis and the release of phage progeny.
On the other hand, many phages will have tail lysins which are required for digestion of bacterial cell wall prior to phage DNA injection. In the case of Gram+ bacteria, phages need to locally disrupt bacterial peptidoglycan prior to DNA injection in the cell and that is done with tail lysins. There might be more then one tail lysin per phage genome and often, they are part of a functional tail fiber or other tail component.
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