Crosstide [GRPRTSSFAEG]

Product Name: Crosstide [GRPRTSSFAEG]

Sequence One Letter Code: GRPRTSSFAEG

Sequence Three Letter Code: H-Gly-Arg-Pro-Arg-Thr-Ser-Ser-Phe-Ala-Glu-Gly-OH

Cas No: 171783-05-4

Chemical Formula:C48H77N17O17

Molecular Weight: 1164.3

Purity: 95%

Form: Lyophilized

Storage Conditions: - 20 °C

Research Area: peptide substrate

SMILES: C[C@H]([C@@H](C(=O)N[C@@H](CO)C(=O)N[C@@H](CO)C(=O)N[C@@H](CC1=CC=CC=C1)C(=O)N[C@@H](C)C(=O)N[C@@H](CCC(=O)O)C(=O)NCC(=O)O)NC(=O)[C@H](CCCN=C(N)N)NC(=O)[C@@H]2CCCN2C(=O)[C@H](CCCN=C(N)N)NC(=O)CN)O

IUPAC: (4S)-4-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-[[(2S,3R)-2-[[(2S)-2-[[(2S)-1-[(2S)-2-[(2-aminoacetyl)amino]-5-(diaminomethylideneamino)pentanoyl]pyrrolidine-2-carbonyl]amino]-5-(diaminomethylideneamino)pentanoyl]amino]-3-hydroxybutanoyl]amino]-3-hydroxypropanoyl]amino]-3-hydroxypropanoyl]amino]-3-phenylpropanoyl]amino]propanoyl]amino]-5-(carboxymethylamino)-5-oxopentanoic acid

INCHIKEY: KJAXEBRGQOHHOY-VXRVIWLSSA-N

INCHI:

InChI=1S/C48H77N17O17/c1-24(38(74)59-28(14-15-35(70)71)39(75)56-21-36(72)73)57-41(77)30(19-26-9-4-3-5-10-26)61-42(78)31(22-66)62-43(79)32(23-67)63-45(81)37(25(2)68)64-40(76)27(11-6-16-54-47(50)51)60-44(80)33-13-8-18-65(33)46(82)29(58-34(69)20-49)12-7-17-55-48(52)53/h3-5,9-10,24-25,27-33,37,66-68H,6-8,11-23,49H2,1-2H3,(H,56,75)(H,57,77)(H,58,69)(H,59,74)(H,60,80)(H,61,78)(H,62,79)(H,63,81)(H,64,76)(H,70,71)(H,72,73)(H4,50,51,54)(H4,52,53,55)/t24-,25+,27-,28-,29-,30-,31-,32-,33-,37-/m0/s1

Source / Species: Drosophila

Conjugation: Unconjugated

Code Nacres: NA.26

Application: Crosstide [GRPRTSSFAEG] is a synthetic peptide substrate derived from glycogen synthase kinase-3 and widely applied in serine/threonine kinase research. It serves as a well-characterized substrate for Akt/protein kinase B and demonstrates comparable specificity toward PKBα, PKBβ, and PKBγ isoforms. Crosstide is also efficiently phosphorylated by MAPKAP kinase-1 and p70S6 kinase, supporting its use in broader kinase profiling and pathway analysis. The defined phosphorylation site enables reliable measurement of kinase catalytic activity in biochemical assays. Modified variants, including fluorescently labeled and biotinylated forms, retain similar enzymatic properties while enabling alternative detection platforms. Crosstide is commonly used for kinetic characterization, substrate competition studies, and inhibitor screening in cell signaling research. Its compatibility with radiometric, colorimetric, and fluorescence-based assays makes it a versatile tool for investigating Akt-dependent signaling, metabolic regulation, and phosphorylation-mediated control of cellular growth and survival pathways.

Current Research: Crosstide (GRPRTSSFAEG) is a synthetic serine/threonine peptide substrate originally derived from glycogen synthase kinase-3–related sequence motifs and is widely used in kinase signaling research. It functions as a well-characterized substrate for Akt, also known as protein kinase B (PKB), and exhibits comparable specificity toward the PKBα (Akt1), PKBβ (Akt2), and PKBγ (Akt3) isoforms. Its defined phosphorylation motif and reproducible enzymatic behavior have established Crosstide as a standard reagent for monitoring Akt catalytic activity in vitro. Akt is a central regulator of cell growth, metabolism, survival, and proliferation. Activated downstream of phosphoinositide 3-kinase (PI3K), Akt phosphorylates numerous substrates involved in glucose metabolism, protein synthesis, apoptosis suppression, and cell cycle progression. Given its pivotal role in oncogenic transformation and metabolic disease, precise quantification of Akt activity is essential for both mechanistic studies and drug discovery applications. Crosstide provides a streamlined substrate system that enables direct assessment of kinase-dependent phosphorylation without the complexity of full-length protein substrates. The peptide contains a defined serine residue within an Akt consensus phosphorylation sequence, allowing efficient catalytic turnover in biochemical assays. Because the phosphorylation site is well characterized, Crosstide supports accurate measurement of kinase activity across a range of enzyme concentrations and assay conditions. Determination of kinetic parameters such as Km and Vmax is readily achieved, facilitating detailed characterization of Akt isoform activity and regulatory modulation. In addition to Akt, Crosstide is efficiently phosphorylated by MAPKAP kinase-1 (also known as RSK) and p70S6 kinase. This cross-reactivity broadens its utility in kinase profiling and pathway analysis, particularly in studies examining signaling cross-talk between PI3K/Akt and MAPK cascades. By applying Crosstide in parallel assays with selective inhibitors or isoform-specific kinases, researchers can dissect pathway contributions and define relative substrate preferences. Crosstide is compatible with multiple detection platforms, including radiometric phosphate incorporation assays, phospho-specific antibody detection, and fluorescence- or colorimetric-coupled readouts. This versatility supports adaptation to diverse laboratory workflows, from low-throughput mechanistic experiments to higher-throughput compound screening. Modified variants, including fluorescently labeled or biotinylated forms, retain similar enzymatic properties while enabling alternative detection strategies such as fluorescence polarization or affinity capture. In drug discovery research, Crosstide is widely used to evaluate Akt inhibitors and modulators targeting downstream kinases within the PI3K/Akt/mTOR axis. By measuring reductions in peptide phosphorylation, investigators can determine inhibitor potency, selectivity, and mechanism of action. The peptide’s reproducibility and compatibility with microplate-based formats make it well suited for screening campaigns and structure–activity relationship studies. Beyond oncology, Crosstide supports investigation of Akt-dependent metabolic regulation, including insulin signaling and glucose homeostasis. Akt-mediated phosphorylation events are central to glycogen synthesis, lipid metabolism, and cell survival pathways. By enabling precise measurement of serine/threonine kinase activity, Crosstide contributes to understanding phosphorylation-mediated control of cellular growth and stress responses. Overall, Crosstide (GRPRTSSFAEG) is a versatile and well-established substrate for serine/threonine kinase research. Its defined phosphorylation site, compatibility with diverse assay formats, and applicability across multiple kinase families make it a valuable tool for mechanistic signaling studies, kinetic characterization, and therapeutic development targeting Akt and related pathways.