MT-CYB

Chr MT

mitochondrially encoded cytochrome b

ENSG00000198727 UniProt: P00156 OMIM: 516020

Cytochrome b is the only mitochondrial DNA-encoded subunit of Complex III of the respiratory chain, serving as the catalytic core for ubiquinol:cytochrome c oxidoreductase activity. Mutations cause Complex III deficiency presenting with exercise intolerance, cardiomyopathy, or MELAS-like syndrome. Inheritance is maternal through the mitochondrial genome, with phenotypic severity depending on the degree of heteroplasmy.

OMIM ResearchSummary from Curated mito context

Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex) that is part of the mitochondrial respiratory chain. The b-c1 complex mediates electron transfer from ubiquinol to cytochrome c. Contributes to the generation of a proton gradient across the mitochondrial membrane that is then used for ATP synthesis

OMIM ResearchGenerating clinical summary…

Primary Disease Associations & Inheritance

UniProtCardiomyopathy, infantile histiocytoid

UniProtLeber hereditary optic neuropathy

Clinical highlights

Gene–disease validity (ClinGen)

Definitive · mitochondrial disease · MT · ClinGen 2024

Active trials

Pubs (1 yr)

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P/LP submissions

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P/LP missense

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LOEUF

Multiple*

Mechanism· predicted

Some data sources returned errors (1)

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Nuclear-gene analyses omitted

MT-CYB is a mitochondrial protein-coding gene. gnomAD constraint, carrier burden and exome coverage, the ClinVar type breakdown, AlphaFold and transcript-architecture views are built for nuclear genes and are not shown. Population data for mtDNA variants (gnomAD v3.1, homoplasmy and heteroplasmy) is on each variant page.

Where it sits in the mitochondrial genome

Tap or hover a gene, landmark or tick; genes open their page, ticks their variant.

proteinrRNAtRNAouter ring H-strand · inner L-strandMITOMAP confirmedreported (as of 2026-10-07)

37 genes from Ensembl (rCRS numbering, matched to MITOMAP’s Gene Loci); landmarks and disease alleles from MITOMAP (CC BY 3.0). Circular layout after MitoWheel.

ClinVar

No ClinVar data available.

Protein Context — Lollipop Plot

MT-CYB · protein map & ClinVar variants

Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.

MITOMAP Disease Variants — MT-CYB

Live table ↗

Variant	AA	Disease	Status	GenBank seqs
m.14783T>C	L13L	Possible role in high altitude sickness	Reported	13,825
m.14787TTAA>-	frameshift	PD / MELAS	Likely pathogenic · confirmed	0
m.14831G>A	A29T	LHON	Reported	124
m.14841A>G	N32S	LHON helper mut.	Reported	21
m.14846G>A	G34S	EXIT / possibly antiatherogenic, poss. myocardial infarction association	Uncertain significance · reported	0
m.14849T>C	S35P	EXIT / Septo-Optic Dysplasia	Uncertain significance · confirmed	0
m.14864T>C	C40R	MELAS	Reported	3
m.14894T>C	F50L	LHON	Reported	14
m.14924T>C	S60P	Mitochondrial neuromuscular disease	Reported	7
m.14970A>G	Y75C	LHON	Reported	7
m.15024G>A	C93Y	Possible DEAF modifier	Reported	40
m.15043G>A	G99G	MDD-associated / possible factor in high altitude sickness / PCOS patient	Reported	15,343
m.15045G>A	R100Q	EXIT	Reported	1
m.15059G>A	G105Term	MM / carotid atherosclerosis risk / essential hypertension	Reported	0
m.15060G>A	G105E	Mitochondrial Respiratory Chain Disorder	Reported	0
m.15077G>A	E111K	DEAF / LHON / helper mutation for maternally inherited hypertension / PCOS patient	Reported	164
m.15084G>A	W113Term	EXIT	Reported	0
m.15092G>A	G116S	MELAS	Reported	0
m.15150G>A	W135Term	EXIT	Likely pathogenic · confirmed	0
m.15153G>A	G136D	Suspected mito disease	Reported	6
m.15158A>G	M138V	Suspected mito disease	Reported	0
m.15168G>A	W141Term	EXIT	Reported	0
m.15170G>A	G142Term	EXIT	Reported	0
m.15197T>C	S151P	EXIT	Uncertain significance · reported	0
m.15200G>T	A152S	Possible factor in sepsis	Reported	0
m.15209T>C	Y155H	Prader-Willi syndrome	Reported	8
m.15215G>A	G157Term	MELAS	Reported	0
m.15218A>G	T158A	Possible LHON modulator	Reported	1,145
m.15234G>A	W163Term	Leigh stroke-like leukodystrophy	Reported	0
m.15236A>G	I164V	Possible LHON helper (one 11778 patient)	Reported	955
m.15237T>C	I164T	Potentially functional variant cosegregating with LHON3635A	Reported	7
m.15242G>A	G166Term	Mitochondrial Encephalomyopathy	Likely pathogenic · confirmed	0
m.15243G>A	G166E	HCM	Reported	0
m.15246G>A	G167D	Mitochondrial Respiratory Chain Disorder	Reported	0
m.15256A>G	V170V	Peripheral neuropathy of T2 diabetes	Reported	4
m.15257G>A	D171N	LHON	Conflicting reports	971
m.15287T>C	F181L	Possible DEAF helper mut.	Reported	126
m.15301G>A	L185L	Possible factor in high altitude sickness, LHON	Reported	19,221
m.15324C>G	A193G	Possible LHON helper (one 11778 patient)	Reported	0
m.15347C>T	H201Y	HCM +LA +elevated CSF lactate	Reported	0
m.15350G>A	E202K	Possible sepsis factor	Reported	0
m.15395A>G	K217E	Possible LHON factor	Reported	3
m.15436C>A	L230L	Possible role in high altitude sickness	Reported	3
m.15453T>C	L236P	Isolated complex III deficiency	Reported	12
m.15485C>T	P247S	Suspected mitochondrial disorder	Reported	0
m.15497G>A	G251S	EXIT / Obesity	Reported	351
m.15498G>A	G251D	DEAF / Infantile histiocytoid cardiomyopathy	Reported	35
m.1549824bp_deletion>	GDPDNYTL-del	EXIT	Reported	0
m.15579A>G	Y278C	Multisystem Disorder, EXIT	Uncertain significance · confirmed	0
m.15615G>A	G290D	EXIT / Antimycin resistance	Uncertain significance · reported	0
m.15620C>A	L292I	Leigh Syndrome helper mut	Reported	0
m.15635T>C	S297P	Polyvisceral failure / adult Leigh syndrome	Reported	2
m.1564918bp_deletion>	ILAMIP-del	Multisystem Disorder, EXIT	Reported	0
m.15662A>G	I306V	Complex mitochondriopathy-associated	Reported	212
m.15674T>C	S310P	LHON	Reported	203
m.15693T>C	M316T	Possibly LVNC cardiomyopathy-associated	Reported	777
m.15699G>C	R318P	Muscle Weakness SNHL and Migraine	Reported	0
m.15723G>A	W326Term	EXIT	Reported	0
m.15761G>A	G339Term	MM	Reported	0
m.15762G>A	G339E	MM	Reported	0
m.15773G>A	V343M	LHON	Reported	83
m.15784T>C	P346P	POAG - potential for association	Reported	2,340
m.15800C>T	Q352Term	EXIT / Myopathy	Reported	0
m.15804T>C	V353A	Fibromyalgia	Reported	39
m.15812G>A	V356M	LHON	Reported	553