The four proteins encoded by the mamXY operon may have a close relationship The qPCR results showed that the four genes in the mamXY operon were all highly expressed during the log phase of growth, supporting previous findings that the log phase is an essential period for MMP function and magnetosome synthesis [31]. The expression of mamZ was much higher than that of the other three genes at each of the sampling times (Figure 5; Table 2), indicating that mamZ plays
a crucial role during growth. MamZ is a highly hydrophobic protein with a predicted weight of 71.7 kDa and contains a major facilitator superfamily domain (predicted by PROSITE), a ferric reductase-like transmembrane component (Pfam; http://pfam.janelia.org/search), and up to 17 transmembrane helices (HMMTOP; http://www.enzim.hu/hmmtop). P005091 It is therefore possible that MamZ is involved in ferric iron reduction, although there is no direct experimental evidence to date for such a function. The results of the relative qPCR assay indicated that deletion of mamX resulted in a notable increase in mamY and ftsZ-like transcription but had no effect on mamZ transcription. These findings suggest some redundancy among the functions of mamX, mamY, and ftsz-like. Application of the online tool STRING (http://string-db.org)
predicted interactions among the four proteins encoded Batimastat in vitro by the mamXY operon (Additional file 2: Figure S2). According to this predicted network view, the four MamXY proteins undergo intrinsic interactions with each other and are also associated
with certain proteins related to cell division (MGR-2076, MGR-3226, MGR-1090, MGR-2217) and to cell wall formation (MGR-0063, MGR-1112, MGR-1092, MGR-2078, MGRGRv1-0136, MGRGRv1-0133) through FtsZ-like. These associated proteins in strain AMB-1 have predicted functions similar to those in MSR-1(Additional file 3: Table S1). Further experiments are needed to test this model. Interestingly, the phenotypes of a mamX mutant, ftsZ-like mutant, and mamXY operon deleted mutant in MSR-1 are similar in that they produce magnetosomes that are small and irregularly shaped in comparison with those of WT [16, 18]. In view of the previous finding that MamGFDC Astemizole proteins have partially redundant and collective functions in controlling magnetosome size [11], and the results of the present study, we propose that the four genes in the mamXY operon have redundant functions involved in the complex process of magnetosome formation. A recent study showed that a single deletion of the mamAB operon in MSR-1 resulted in the complete loss of magnetosome synthesis, whereas deletion of the conserved mms6, mamGFDC, and mamXY operons led to severe defects in the morphology, size, and Selleckchem SHP099 organization of magnetite crystals [16]. The MamP, MamS, MamR, and MamT proteins were shown to function in the regulation of crystal number, size, and shape [14].