9.B.106 The Pock Size-determining Protein (PSDP) Family

The pock size-determining protein, SpdB, is encoded on plasmid pSN22 (Kataoka et al., 1991a). It may enhance efficiency of plasmid transfer (Kataoka et al., 1991b). It is under TraR control and has 325 aas and 4 N-terminal TMSs. Four SpdB proteins (SpdB1-SpdB4) have been idntified (Kataoka et al., 1994). The C-terminal hydrophilic domain is an Ala/Glu-rich domain that is similar to domains in other proteins such as TolA of E. coli (TC# 1.A.30.2.2). The SpdA (TC# 9.B.106.2.1) and SpdB proteins may function together. It appears that families 9.B.54, 9.B.106, and 9.B.148, all containing 4 TMS members, may be homologous.

This family belongs to the Protein Kinase (PK) Superfamily.



Das, S. and E. Knust. (2017). Stardust, the Janus-faced partner of Crumbs. J. Cell Biol. 216: 1219-1221.

Kataoka, M., T. Seki, and T. Yoshida. (1991). Five genes involved in self-transmission of pSN22, a Streptomyces plasmid. J. Bacteriol. 173: 4220-4228.

Kataoka, M., T. Seki, and T. Yoshida. (1991). Regulation and function of the Streptomyces plasmid pSN22 genes involved in pock formation and inviability. J. Bacteriol. 173: 7975-7981.

Kataoka, M., Y.M. Kiyose, Y. Michisuji, T. Horiguchi, T. Seki, and T. Yoshida. (1994). Complete nucleotide sequence of the Streptomyces nigrifaciens plasmid, pSN22: genetic organization and correlation with genetic properties. Plasmid 32: 55-69.

Lin, H., W. Du, Y. Yang, K.S. Schumaker, and Y. Guo. (2014). A calcium-independent activation of the Arabidopsis SOS2-like protein kinase24 by its interacting SOS3-like calcium binding protein1. Plant Physiol. 164: 2197-2206.

Mendes, M.V., J.F. Aparicio, and J.F. Martín. (2000). Complete nucleotide sequence and characterization of pSNA1 from pimaricin-producing Streptomyces natalensis that replicates by a rolling circle mechanism. Plasmid 43: 159-165.


TC#NameOrganismal TypeExample

The pock size-determining protein, SpdB


SpdB of Streptomyces coelicolor (Q9F2T7)


gp25 phage protein

Actinobacterial Phage

gp25 of Streptomyces phage phiBT1 (Q858X7)


Putative plasmid transfer protein, SpdB2. Residues 191-443 give e-17 with TolA (2.C.1.2.1) residues 59-315, both being A+E-rich domains. Many other proteins in TCDB also have this hydrophilic domain.


SpdB2 of Streptomyces rochei (F2Z8Q7)


SPW repeat protein of 119 aas and 4 TMSs, Gp25


SPW repeat protein, Gp25, of Rhizobium mesoamericanum


Uncharacterized protein of 205 aas and 4 TMSs

UP of Saccharothrix espanaensis


Uncharacterized protein of 133 aas and 4 TMSs.

UP of Kutzneria albida


TC#NameOrganismal TypeExample

TC#NameOrganismal TypeExample

TC#NameOrganismal TypeExample