Rcf1 Mediates Cytochrome Oxidase Assembly and Respirasome Formation, Revealing Heterogeneity of the Enzyme Complex

Abstract

The terminal enzyme of the mitochondrial respiratory chain, cytochrome oxidase, transfers electrons to molecular oxygen, generating water. Within the inner mitochondrial membrane, cytochrome oxidase assembles into supercomplexes, together with other respiratory chain complexes, forming so-called respirasomes. Little is known about how these higher oligomeric structures are attained. Here we report on Rcf1 and Rcf2 as cytochrome oxidase subunits in S. cerevisiae. While Rcf2 is specific to yeast, Rcf1 is a conserved subunit with two human orthologs, RCF1a and RCF1b. Rcf1 is required for growth in hypoxia and complex assembly of subunits Cox13 and Rcf2, as well as for the oligomerization of a subclass of cytochrome oxidase complexes into respirasomes. Our analyses reveal that the cytochrome oxidase of mitochondria displays intrinsic heterogeneity with regard to its subunit composition and that distinct forms of respirasomes can be formed by complex variants.

Arrangement of the Respiratory Chain Complexes in Saccharomyces cerevisiae Supercomplex III2IV2 Revealed by Single Particle Cryo-Electron Microscopy

“…On the other hand, we cannot exclude the possibility that several Rcf1 proteins can provide a connection between individual complexes through an interaction of their coiled coil domains exposed to the inter-membrane space. Since digitonin extracted supercomplex contains these proteins (42)(43)(44), they must be present in our purified supercomplex and for example may be responsible for the protrusion exposed to the inter-membrane space. Further structural studies are required to identify the location of the Rcf proteins in the supercomplex structure.…”

“…Recent reports indicate that in addition to CL two related proteins, Rcf1 and Rcf2, are also important for supercomplex formation and stability (42)(43)(44). These are small proteins of about 20 kDa containing two transmembrane domains.…”

A stabilizing factor for mitochondrial respiratory supercomplex assembly regulates energy metabolism in muscle

“…Recently, respiratory supercomplex factor 1 (Rcf1) and its homologue Rcf2 have been identified in yeast as factors required for the normal assembly and complete enzymatic activity of complex IV [19][20][21] . Rcf1 and Rcf2 are both required for complete complex IV assembly and enzyme activity.…”

Respiratory-deficient mutants of the unicellular green alga Chlamydomonas: A review

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 16 [17], (c) [68], (d) [69], (e) [70], (f) [71], (g) [72], (h) [73], (i) [74], (j) [75], (k) [76], (l) [77], (m) [22], (n) [29], (o) [78], (p) [58], (q) [79], (r)[34] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 17 ((a) [48], (b) [45], (c) [47], (d) [43], (e) [44], (f) [39], (g) …”