The domain within your query sequence starts at position 2 and ends at position 87; the E-value for the SRP54_N domain shown below is 7.47e-19.

VLADLGRKITSALRSLSNATIINEEVLNAMLKEVCTALLEADVNIKLVKQLRENVKSAID
LEEMASGLNKRKMIQHAVFKELVKLV

SRP54_N

SRP54-type protein, helical bundle domain

• SMART accession number: SM00963
• Description: This entry represents the N-terminal helical bundle domain of the 54 kDa SRP54 component, a GTP-binding protein that interacts with the signal sequence when it emerges from the ribosome. SRP54 of the signal recognition particle has a three-domain structure: an N-terminal helical bundle domain, a GTPase domain, and the M-domain that binds the 7s RNA and also binds the signal sequence. The extreme C-terminal region is glycine-rich and lower in complexity and poorly conserved between species.
• Interpro abstract (IPR013822):

  This entry represents the N-terminal helical bundle domain of the 54kDa SRP54 component, a GTP-binding protein that interacts with the signal sequence when it emerges from the ribosome. SRP54 of the signal recognition particle has a three-domain structure: an N-terminal helical bundle domain, a GTPase domain, and the M-domain that binds the 7s RNA and also binds the signal sequence. The extreme C-terminal region is glycine-rich and lower in complexity and poorly conserved between species.

  Other proteins with this domain include signal recognition particle receptor alpha subunit (docking protein), an integral membrane GTP-binding protein which ensures (in conjunction with SRP) the correct targeting of nascent secretory proteins to the endoplasmic reticulum membrane; and bacterial FtsY protein, which is believed to play a similar role to that played by the eukaryotic docking protein.

• GO process: SRP-dependent cotranslational protein targeting to membrane (GO:0006614)
• GO function: GTP binding (GO:0005525)

There are 40739 SRP54_N domains in 40723 proteins in SMART's nrdb database.

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Montoya G, Svensson C, Luirink J, Sinning I
• Crystal structure of the NG domain from the signal-recognition particlereceptor FtsY.
• Nature. 1997; 385: 365-8

Newly synthesized proteins destined either for secretion or incorporationinto membranes are targeted to the membrane translocation machinery by aubiquitous system consisting of a signal-recognition particle (SRP) andits receptor. Both the SRP receptor and the protein within the SRP thatbinds the signal sequence contain GTPases. These two proteins, togetherwith the RNA component of the SRP, form a complex and thereby regulateeach other's GTPase activity. Here we report the structure of theGTPase-containing portion of FtsY, the functional homologue of the SRPreceptor of Escherichia coli, at 2.2 A resolution without boundnucleotide. This so-called NG domain displays similarities to theRas-related GTPases, as well as features unique to the SRP-type GTPases,such as a separate amino-terminal domain, an insertion within the p21ras(Ras) effector domain, and a wide-open GTP-binding region. The structureexplains the low affinity of FtsY for GTP, and suggests rearrangementsthat may occur on nucleotide binding. It also identifies regionspotentially involved in the transmission of signals between domains and ininteractions with regulatory proteins.

Structure (3D structures containing this domain)

3D Structures of SRP54_N domains in PDB

PDB code	Title
1ffh	N AND GTPASE DOMAINS OF THE SIGNAL SEQUENCE RECOGNITION PROTEIN FFH FROM THERMUS AQUATICUS
1fts	SIGNAL RECOGNITION PARTICLE RECEPTOR FROM E. COLI
1j8m	Signal Recognition Particle conserved GTPase domain from A. ambivalens
1j8y	Signal Recognition Particle conserved GTPase domain from A. ambivalens T112A mutant
1jpj	GMPPNP Complex of SRP GTPase NG Domain
1jpn	GMPPNP Complex of SRP GTPase NG Domain
1ls1	T. aquaticus Ffh NG Domain at 1.1A Resolution
1ng1	N AND GTPASE DOMAINS OF THE SIGNAL SEQUENCE RECOGNITION PROTEIN FFH FROM THERMUS AQUATICUS
1o87	A new MgGDP complex of the Ffh NG domain
1okk	HOMO-HETERODIMERIC COMPLEX OF THE SRP GTPASES
1qzw	Crystal structure of the complete core of archaeal SRP and implications for inter-domain communication
1qzx	Crystal structure of the complete core of archaeal SRP and implications for inter-domain communication
1rj9	Structure of the heterodimer of the conserved GTPase domains of the Signal Recognition Particle (Ffh) and Its Receptor (FtsY)
1ry1	Structure of the signal recognition particle interacting with the elongation-arrested ribosome
1vma	Crystal structure of Cell division protein ftsY (TM0570) from Thermotoga maritima at 1.60 A resolution
1wgw	Solution Structure of the N-terminal Domain of Mouse Putative Signal Recoginition Particle 54 (SRP54)
1zu4	Crystal structure of FtsY from Mycoplasma mycoides- space group P21212
1zu5	Crystal structure of FtsY from Mycoplasma mycoides- space group H32
2c03	GDP COMPLEX OF SRP GTPASE FFH NG DOMAIN
2c04	GMPPCP complex of SRP GTPase Ffh NG Domain at ultra-high resolution
2cnw	GDPALF4 complex of the SRP GTPases Ffh and FtsY
2ffh	THE SIGNAL SEQUENCE BINDING PROTEIN FFH FROM THERMUS AQUATICUS
2iy3	Structure of the E. Coli Signal Regognition Particle
2j28	Model of E. coli SRP bound to 70S RNCs
2j37	Model of Mammalian SRP bound to 80s RNCs
2j45	Water structure of T. Aquaticus Ffh NG Domain At 1.1A Resolution
2j46	Water structure of T. Aquaticus Ffh NG Domain At 1.1A Resolution
2j7p	GMPPNP-stabilized NG domain complex of the SRP GTPases Ffh and FtsY
2ng1	N AND GTPASE DOMAINS OF THE SIGNAL SEQUENCE RECOGNITION PROTEIN FFH FROM THERMUS AQUATICUS
2og2	Crystal structure of chloroplast FtsY from Arabidopsis thaliana
2q9a	Structure of Apo FTSY
2q9b	Structure of FTSY:GMPPNP Complex
2q9c	Structure of FTSY:GMPPNP with MGCL Complex
2qy9	Structure of the NG+1 construct of the E. coli SRP receptor FtsY
2v3c	Crystal structure of the SRP54-SRP19-7S.S SRP RNA complex of M. jannaschii
2xkv	Atomic Model of the SRP-FtsY Early Conformation
2xxa	The Crystal Structure of the Signal Recognition Particle (SRP) in Complex with its Receptor(SR)
2yhs	Structure of the E. coli SRP receptor FtsY
3b9q	The crystal structure of cpFtsY from Arabidopsis thaliana
3dm5	Structures of SRP54 and SRP19, the two proteins assembling the ribonucleic core of the Signal Recognition Particle from the archaeon Pyrococcus furiosus.
3dm9	Structures and Conformations in Solution of the Signal Recognition Particle Receptor from the archaeon Pyrococcus furiosus
3dmd	Structures and Conformations in Solution of the Signal Recognition Particle Receptor from the archaeon Pyrococcus furiosus
3e70	Structures and conformations in solution of the Signal Recognition Particle Receptor from the Archaeon Pyrococcus Furiosus
3jaj	3JAJ
3jan	3JAN
3kl4	Recognition of a signal peptide by the signal recognition particle
3ndb	Crystal structure of a signal sequence bound to the signal recognition particle
3ng1	N AND GTPASE DOMAINS OF THE SIGNAL SEQUENCE RECOGNITION PROTEIN FFH FROM THERMUS AQUATICUS
3zn8	Structural Basis of Signal Sequence Surveillance and Selection by the SRP-SR Complex
4ak9	Structure of chloroplast FtsY from Physcomitrella patens
4c7o	The structural basis of FtsY recruitment and GTPase activation by SRP RNA
4ue5	4UE5
5gad	5GAD
5gaf	5GAF
5gag	5GAG
5gah	5GAH
5l3q	5L3Q
5l3r	5L3R
5l3s	5L3S
5l3v	5L3V
5l3w	5L3W

Links (links to other resources describing this domain)

• PFAM: SRP54_N
• INTERPRO: IPR013822