TABLE 1.

Clusters of predicted c-type cytochromes and other heme-containing proteins of interest from MMSeqs2.

Cluster	Functional prediction	# CXXCH, CX3CH, or CX4CH motifs per protein	# FeOB (of 87)
Iron oxidation/reduction proteins
313	Iron oxidase Cyc2‡	1	70
451	Decaheme c-type cytochrome, DmsE family, MtoA‡	10	19
335	Decaheme c-type cytochrome, DmsE family, MtoA‡	10	17
50	Decaheme c-type cytochrome, OmcA/MtrC family†	10	7
Potential EET/EEU pathway proteins
20	Cytochrome C family protein; potential periplasmic PCC3 subunit‡	21, 24, 27	42
241	Cytochrome C family protein; potential extracellular PCC3 subunit‡	10, 11, 12, 13, 14, 15, 16, 18	34
242	Cytochrome C family protein; potential extracellular PCC3 subunit‡	26, 28, 29, 33, 35	7
331	Cytochrome C family protein; potential extracellular PCC3 subunit‡	15, 17	5
65	Doubled CXXCH motif-containing protein; Cytochrome c3 family protein†, potential UetJ subunit	11, 12	6
479	Tetraheme cytochrome - potential UetA subunit	4	6
330	Cytochrome C7 domain-containing protein; Triheme cytochrome - potential UetDEG subunit	3	5
94	Cytochrome C7 domain-containing protein; Triheme cytochrome - potential UetDEG subunit	3	5
446	Diheme cytochrome c‡ - potential Slit_1324	2	51
Sensory proteins
152	Methyl-accepting chemotaxis sensory transducer; YoaH ‡	1	54
40	Methyl-accepting chemotaxis sensory transducer with Pas/Pac sensor; Aerotaxis receptor ‡	1	43
400	Diguanylate cyclase with PAS/PAC sensor; Cyclic di-GMP phosphodiesterase Gmr ‡	1	36
Other
433	2Fe-2S ferredoxin‡	1, 2	72
360	4Fe-4S ferredoxin iron-sulfur binding domain protein	1	41
403	Forkhead-associated protein‡	10	27
146	Cytochrome c; Octaheme tetrathionate reductase‡	8	25
253	Sulfite reductase, dissimilatory-type, subunit DsrJ†	3	17

Functional predictions are based on ‡ isolate annotations and NCBI BLAST or † BLAST of sequences from metagenomes in Uniprot.