9.B.28 The Putative Protease Component of the MusEFGKI ABC Transporter (MusI) Family A maltose transporter, MusEFGKI of Corynebacterium glutamicum is believed to include an extra subunit designated MusI. All five genes (musEFGKI) have been reported to be essential for uptake activity (Henrich et al. 2013). The musI gene product is of 215 aas with 5 TMSs and comprises the founding member of a distinct family of uncharacterized protein in this TC family (MusI; 9.B.28). However members of the family can have 4 - 7 TMSs. Family members are found in bacteria, archaea and eukaryotes and show sequence and topological similarity to members of the rhomboid (TC# 9.B.104) and CAAX2 (9.B.2) protease families. Some members of the MusI family have therefore been transferred to the Rhomboid Protease Family (9.B.104). Proteins of TC family 9.B.28 (particularly 9.B.325.2.6 and 7) show sequence similarity with one of the members of TC family 9.B.325 (9.B.325.1.2) which unlike other members of the 9.B.325 family have either 5 TMS alone, or 10 TMSs with a 5 TMS repeat unit.
This family belongs to the MusI (MusI) Superfamily.
References:
Henrich, A., N. Kuhlmann, A.W. Eck, R. Krämer, and G.M. Seibold. (2013). Maltose uptake by the novel ABC transport system MusEFGK2I causes increased expression of ptsG in Corynebacterium glutamicum. J. Bacteriol. 195: 2573-2584.
Examples:
TC#	Name	Organismal Type	Example
9.B.28.1.1	*MusI of 115 aas and 5 TMSs in a 1 + 2 + 2 arrangement. Mus I has been reported to be an essential consitutent of an ABC-type maltose transporter, MusEFGKI (Henrich et al.* 2013).**	Actinobacteria	MusI of Corynebacterium glutamicum

9.B.28.1.10	MusI homologue of 233 aas and 5 TMSs	Actinobacteria	MusI homologue of Bifidobacterium thermophilum

9.B.28.1.11	MusI homologue of 204 aas and 5 TMSs	Firmicutes	MusI homologue of Streptococcus pneumoniae

9.B.28.1.12	Uncharacterized protein of 206 aas and 6 TMSs	Firmicutes	UP of Streptococcus intermedius

9.B.28.1.13	DUF624 domain protein of 197 aas and 5 TMSs.		DUF624 protein of Enterococcus faecalis

9.B.28.1.14	Uncharacterized DUF624 domain protein of 205 aas and 6 TMSs		UP of Ruminococcus flavefaciens

9.B.28.1.15	YesL family protein of 217 aas and 5 TMSs.		YesL protein of Roseburia hominis

9.B.28.1.16	DUF624 domain-containing protein of 316 aas and 5 TM		DUF624 protein of candidate division Zixibacteria bacterium

9.B.28.1.2	MusI homologue of 203 aas and 5 TMSs.	Firmicutes	MusI homologue of Clostridium phytofermentans

9.B.28.1.3	MusI homologue of 201 aas and 5 TMSs. This protein is encoded within an operon encoding all constituents of a maltose-like ABC transporter except the ATPase (C). The operon also encodes a putative arabinosidase, suggesting that the substrate of this transporter may be arabinose.	Actinobacteria	MusI homologue of Bifidobacterium longum

9.B.28.1.4	MusI homologue of 216 aas and 5 TMSs	Firmictues	MusI homologue of Streptococcus equi

9.B.28.1.5	MusI homologue, YesL, of 207 aas and 5 TMSs	Firmicutes	YesL of Bacillus subtilis

9.B.28.1.6	MusI homologue of 217 aas and 4 TMSs	Euryarchaea	MusI homologue of Halosarcina pallida

9.B.28.1.7	MusI homologue of 236 aas and 4 TMSs	Euryarchaea	MusI homologue of Haloarcula japonicum

9.B.28.1.8	MusI homologue of 321 aas and 5 TMSs	Firmicutes	MusI homologue of Anaerotruneus colihominis

9.B.28.1.9	MusI homologue of 212 aas and 4 TMSs	Spirochaetes	MusI homologue of Sphaerochaeta pleomorpha

Examples:
TC#	Name	Organismal Type	Example
9.B.28.2.1	MusI homologue of 195 aas and 5 TMSs	Euryarchaea	MusI homologue of Methanococcoides burtonii

9.B.28.2.10	UP of 303 aas and 6 TMSs with a C-terminal DZR domain.		UP of Candidatus Bathyarchaeota archaeon B26-1

9.B.28.2.12	Uncharacterized protein of 283 aas and 6 TMSs.		UP of Planctomycetes bacterium (anaerobic digester metagenome)

9.B.28.2.2	MusI homologue of 252 aas and 6 TMSs	Proteobacteria	MusI homologue of Azospira oryzae (Dechlorosoma suillum)

9.B.28.2.3	Uncharacterized protein of 226 aas and 6 TMSs	Chlorobi	UP of Prosthecochloris aestuarii

9.B.28.2.4	Uncharacterized protein of 220 aas and 6 TMSs.		UP of Pseudomonas saponiphila

9.B.28.2.5	DUF975/UPF6259 Family protein of 211 aas and 4 TMSs.		DUF975 protein of Hyphomicrobium sp.

9.B.28.2.6	Uncharacterized DUF975 domain-containing protein of 206 aas and 5 TM		UP of Candidatus Achromatium palustre

9.B.28.2.7	Uncharacterized protein of 245 aas and 4 TMSs in a 2 + 1 + 1 TMS arrangement.		UP of Streptococcus troglodytae

9.B.28.2.8	Uncharacterized protein of 295 aas and 6 TMSs.		*UP of Tenacibaculum* sp.**

9.B.28.2.9	Uncharacterized protein of 295 aas and 5 TMSs.		UP of Candidatus Saccharibacteria bacterium

Examples:
TC#	Name	Organismal Type	Example
9.B.28.3.1	MusI homologue of 223 aas and 6 TMSs	Firmictues	MusI homologue of Enterococcus faecalis

9.B.28.3.2	DUF624 protein of 229 aas and 6 TMSs.		DUF624 protein of Micromonospora narathiwatensis

Examples:
TC#	Name	Organismal Type	Example
9.B.28.4.2	Uncharacterized protein of 231 aas and 6 TMSs.		UP of Rhodothermus profundi

9.B.28.4.3	Uncharacterized putative ABC membrane protein of 269 aas and 6 TMSs.		UP of Streptomyces sp. CB01883

Examples:
TC#	Name	Organismal Type	Example
9.B.28.5.1	Uncharacterized glycerophosphodiester phosphodiesterase of 598 aas with 7 N-terminal TMSs and a C-terminal hydrophilic domain.		UP of Enterococcus aquimarinus

9.B.28.5.10	Uncharacterized protein of 695 aas with 2 N-terminal TMSs, followed by a large hydrophilic domain followed by a transmembrane domain consisting of 8 TMSs in a 2 + 2 + 2 + 2 probable TMS arrangement.		UP of Jiangella ureilytica

9.B.28.5.2	Uncharacterized membrane domain of a glycerophosphoryl diester phosphodiesteraseof 271 aas and 6 TMSs.		UP of Streptococcus pyogenes

9.B.28.5.3	Hydrolase of 670 aas and 6 TMSs		Hydrolase of Porphyromonas crevioricanis

9.B.28.5.4	Uncharacterized membrane-anchored glycerophosphoryl diester phosphodiesterase (GDPDase), membrane domain of 427 aas and 6 or 7 TMSs in a (1? +) 2 + 2 + 2 TMS arrangement..		UP of Microbacterium sp.

9.B.28.5.6	Glycerophosphoryl diester phosphodiesterase membrane domain-containing protein of 450 aas and 6 TMSs.		Phosphodiesterase of Streptomyces olivaceus

9.B.28.5.7	Uncharacterized protein of 372 aas and 6 TMSs		*UP of Cryobacterium* sp.**

9.B.28.5.8	Uncharacterized protein of 308 aas and 6 TMSs		UP of Rossellomorea vietnamensis

9.B.28.5.9	Uncharacterized protein of 302 aas and 6 TMSs		UP of Euryarchaeota archaeon (soil metagenome)

Examples:
TC#	Name	Organismal Type	Example
9.B.28.6.1	Uncharacterized protein of 250 aas and 5 TMSs in a 1 + 2 + 2 TMS arrangement.		UP of Myceligenerans xiligouense

9.B.28.6.2	Poxvirus protein I5 of 210 aas and 5 TMSs in a 1 + 2 + 2 TMS arrangement.		Viral protein of Isoptericola chiayiensis

9.B.28.6.3	DUF624 domain-containing protein of 215 aas and 5 TMSs in a 1 + 2 + 2 TMS arrangement		DUF624 protein of Microbacterium ureisolvens

9.B.28.6.4	Uncharacterized protein of 215 aas and 5 TMSs in a 1 + 2 + 2 TMS arrangement.		*UP of Streptomyces* sp. CS113**

9.B.28.6.5	Uncharacterized protein of 217 aas and 5 TM		UP of Phytomonospora endophytica

Examples:
TC#	Name	Organismal Type	Example
9.B.28.7.1	Uncharacterized protein of 248 aas and 6 TMSs in a 2 + 2 + 2 TMS arrangement.		UP of Kitasatospora cheerisanensis

9.B.28.7.2	Uncharacterized protein of 295 aas and 6 TMSs in a 2 + 2 + 2 TMS arrangement.		UP of Candidatus Prometheoarchaeum syntrophicum

9.B.28.7.3	ABC transporter permease subunit of 632 aas and 13 or 14 putative TMSs in a 6 (2 + 2 + 2) + 1 + 1 + 5 or 6 TMS arrangement. The first 6 TMSs are homologous to other members of this subfamily. The last cluster of TMSs at the C-terminus may be homologous to ABC membrane proteins.		Putative ABC membrane subunit of Halopiger djelfimassiliensis

9.B.28.7.4	Uncharacterized protein of 204 aas and 6 TMSs. The encoding gene is adjacent to a cell wall hydrolase/autolysin gene.		UP of Parcubacteria group bacterium

Examples:
TC#	Name	Organismal Type	Example
9.B.28.8.1	Uncharacterized protein of 419 aas and 6 TMSs		UP of Archaeoglobus fulgidus

9.B.28.8.2	Uncharacterized protein of s362 aas and 6 TMSs.		UP of Methanosarcinales archaeon (marine sediment metagenome)

9.B.28.8.3	Uncharacterized protein of 297 aas and 6 TMSs		UP of Halorubellus salinus

9.B.28.8.4	Uncharacterized protein of 316 aas and 6 TMSs		UP of Candidatus Altiarchaeota archaeon (freshwater sediment metagenome)