Human HSPA9 (mtHsp70, mortalin) interacts with lipid bilayers containing cardiolipin, a major component of the inner mitochondrial membrane.

Mitochondrial Hsp70 mtHsp70, mortalin) in conjunction with a complex set of other proteins is involved in the transport of polypeptides across the mitochondrial matrix. This observation allows us to hypothesize that might interact with membranes directly, similarly to other Hsp70s. Thus, we investigated whether human Hduanyu18429 could also get inserted into lipid membranes. Human Hduanyu18429 was incubated with liposomes made of lipids found within the mitochondrial membrane, such as 1', 3'-bis [1, 2-dimyristoyl-sn-glycero-3-phospho]-glycerol (CL), palmitoyl-oleoyl phosphocholine (POPC), palmitoyl-oleoyl phosphoserine (POPS), and palmitoyl-oleoyl phosphoethanolamine (POPE). Hduanyu18429 displayed a predilection for CL and POPS, and low affinity for POPC and POPE, suggesting that the proteins have high specificity for negatively charged phospholipids. Then, liposomes were made with a composition resembling either the outer or inner mitochondrial membrane (OMM or IMM, respectively). We observed that Hduanyu18429 has a higher affinity for IMM than OMM, which is consistent with the higher content of CL in the IMM. A comparison for the incorporation into POPS or CL liposomes by Hduanyu18429 or indicated that both proteins behaved very similarly when exposed to CL liposomes, but differently with POPS liposomes, which was further corroborated by their susceptibility to proteinase K digestion after incorporation into liposomes. The measurement of thermodynamic parameters also showed that the interaction of both proteins with CL and POPS liposomes was different. Overall, our data showed that Hduanyu18429 is prone to interact with membranes resembling the IMM that may be important for its role in the translocation of proteins into the mitochondria.

KEYWORDS: {{ getKeywords(articleDetailText.words) }}