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M M Zhou

Publications and source records attributed to M M Zhou.

At least 19 recordsLinked to original sources
PubMed2001

Solution structure of ERK2 binding domain of MAPK phosphatase MKP-3: structural insights into MKP-3 activation by ERK2.

MAP kinases (MAPKs), which control mitogenic signal transduction in all eukaryotic organisms, are inactivated by dual specificity MAPK phosphatases (MKPs). MKP-3, a prototypical MKP, achieves substrate specificity through its N-terminal domain binding to the MAPK ERK2, resulting in the activation of its C-terminal phosphatase domain. The solution structure and biochemical analysis of the ERK2 binding (EB) domain of MKP-3 show that regions that are essential for ERK2 binding partly overlap with its sites that interact with the C-terminal catalytic domain, and that these interactions are functionally coupled to the active site residues of MKP-3. Our findings suggest a novel mechanism by which the EB domain binding to ERK2 is transduced to cause a conformational change of the C-terminal catalytic domain, resulting in the enzymatic activation of MKP-3.

Amino Acid Sequence↗
PubMed2001

Alteration of orphanin FQ immunoreactivity and ppOFQ mRNA by combination of melatonin with electroacupuncture.

The aim of the present study was to observe the alternation of central orphanin FQ (OFQ, also known as nociceptin) system while electroacupuncture (EA) combined with melatonin (MEL). The experiments were carried out to investigate the changes of OFQ-like immunoreactivity and prepro-orphanin FQ (ppOFQ) mRNA in some certain nuclei of the rat brain. Using immunohistochemical technique we found that the level of OFQ-like immunoreactivity was increased significantly in some pain-modulation-related nuclei, such as ventromedial hypothalamic nucleus, raphe magnus nucleus, dorsal raphe nucleus and periaqueductal gray (PAG) after intraperitoneal (i.p.) injection of MEL 60 mg/kg, and it was further enhanced while MEL combined with EA. By using in situ hybridization, we found that ppOFQ mRNA expression was decreased in the same nuclei after the administration of MEL, and further decreased following the combination of EA and MEL. The results suggested that attenuating the release and synthesis of OFQ in the brain is one of the mechanisms that melatonin promotes acupuncture analgesia.

Acupuncture Analgesia↗
PubMed2001

[Changes of cerebral beta-endorphin in rats treated with combination therapy of melatonin and electroacupuncture].

OBJECTIVE: To explore the strengthening of acupuncture analgesic mechanism on the level of beta-endorphin and proopimelanocortin mRNA expression in the arcuate nucleus of hypothalamus in rats following electroacupuncture (EA) combined with melatonin (MEL). METHODS: Integrated optical density (IOD) was measured by ABC immuno-histochemical and in situ hybridization technique with computerized image processing. The rat's brain was coronally sectioned after combination of EA and MEL. RESULTS: IOD of beta-endorphin-like immunopositive substance in rat's brain was lowered significantly, which was measured after MEL (60 mg/kg) was injected intraperitoneally and followed by EA 30 min later for 30 min, and the IOD of cerebral POMC mRNA positive substance increased significantly 10 hrs later. CONCLUSION: The mechanism of MEL in enhancing EA analgesic effect might be related with the release and synthesis of beta-endorphin.

Acupuncture Analgesia↗
PubMed2000

The rat liver Na(+)/bile acid cotransporter. Importance of the cytoplasmic tail to function and plasma membrane targeting.

To understand the potential functions of the cytoplasmic tail of Na(+)/taurocholate cotransporter (Ntcp) and to determine the basolateral sorting mechanisms for this transporter, green fluorescent protein-fused wild type and mutant rat Ntcps were constructed and the transport properties and cellular localization were assessed in transfected COS 7 and Madin-Darby canine kidney (MDCK) cells. Truncation of the 56-amino acid cytoplasmic tail demonstrates that the cytoplasmic tail of rat Ntcp is involved membrane delivery of this protein in nonpolarized and polarized cells and removal of the tail does not affect the bile acid transport function of Ntcp. Using site-directed mutagenesis, two tyrosine residues, Tyr-321 and Tyr-307, in the cytoplasmic tail of Ntcp have been identified as important for the basolateral sorting of rat Ntcp in transfected MDCK cells. Tyr-321 appears to be the major basolateral-sorting determinant, and Tyr-307 acts as a supporting determinant to ensure delivery of the transporter to the basolateral surface, especially at high levels of protein expression. When the two Tyr-based basolateral sorting motifs have been removed, the N-linked carbohydrate groups direct the tyrosine to alanine mutants to the apical surface of transfected MDCK cells. The major basolateral sorting determinant Tyr-321 is within a novel beta-turn unfavorable tetrapeptide Y(321)KAA, which has not been found in any naturally occurring basolateral sorting motifs. Two-dimensional NMR spectroscopy of a 24-mer peptide corresponding to the sequence from Tyr-307 to Thr-330 on the cytoplasmic tail of Ntcp confirms that both the Tyr-321 and Tyr-307 regions do not adopt any turn structure. Since the major motif YKAA contains a beta-turn unfavorable structure, the Ntcp basolateral sorting may not be related to the clathrin-adaptor complex pathway, as is the case for many basolateral proteins.

Amino Acid Sequence↗
PubMed2000

Structural basis of SNT PTB domain interactions with distinct neurotrophic receptors.

SNT adaptor proteins transduce activation of fibroblast growth factor receptors (FGFRs) and neurotrophin receptors (TRKs) to common signaling targets. The SNT-1 phosphotyrosine binding (PTB) domain recognizes activated TRKs at a canonical NPXpY motif and, atypically, binds to nonphosphorylated FGFRs in a region lacking tyrosine or asparagine. Here, using NMR and mutational analyses, we show that the PTB domain utilizes distinct sets of amino acid residues to interact with FGFRs or TRKs in a mutually exclusive manner. The FGFR1 peptide wraps around the beta sandwich structure of the PTB domain, and its binding is possibly regulated by conformational change of a unique C-terminal beta strand in the protein. Our results suggest mechanisms by which SNTs serve as molecular switches to mediate the essential interplay between FGFR and TRK signaling during neuronal differentiation.

Adaptor Proteins, Signal Transducing↗
PubMed1999

NMR-based discovery of phosphotyrosine mimetics that bind to the Lck SH2 domain.

Using an NMR-based screen, a series of novel phosphotyrosine mimetics were discovered that bind to the SH2 domain of Lck. These compounds may serve as useful leads for the design of nonpeptide inhibitors of SH2 domains with improved bioavailability and metabolic stability compared to the natural ligands that contain phosphotyrosine.

Magnetic Resonance Spectroscopy↗
PubMed1999

Structure and ligand of a histone acetyltransferase bromodomain.

Histone acetylation is important in chromatin remodelling and gene activation. Nearly all known histone-acetyltransferase (HAT)-associated transcriptional co-activators contain bromodomains, which are approximately 110-amino-acid modules found in many chromatin-associated proteins. Despite the wide occurrence of these bromodomains, their three-dimensional structure and binding partners remain unknown. Here we report the solution structure of the bromodomain of the HAT co-activator P/CAF (p300/CBP-associated factor). The structure reveals an unusual left-handed up-and-down four-helix bundle. In addition, we show by a combination of structural and site-directed mutagenesis studies that bromodomains can interact specifically with acetylated lysine, making them the first known protein modules to do so. The nature of the recognition of acetyl-lysine by the P/CAF bromodomain is similar to that of acetyl-CoA by histone acetyltransferase. Thus, the bromodomain is functionally linked to the HAT activity of co-activators in the regulation of gene transcription.

Acetyltransferases↗
PubMed1999

Phosphotyrosine binding domains of Shc and insulin receptor substrate 1 recognize the NPXpY motif in a thermodynamically distinct manner.

Phosphotyrosine binding (PTB) domains of the adaptor protein Shc and insulin receptor substrate (IRS-1) interact with a distinct set of activated and tyrosine-phosphorylated cytokine and growth factor receptors and play important roles in mediating mitogenic signal transduction. By using the technique of isothermal titration calorimetry, we have studied the thermodynamics of binding of the Shc and IRS-1 PTB domains to tyrosine-phosphorylated NPXY-containing peptides derived from known receptor binding sites. The results showed that relative contributions of enthalpy and entropy to the free energy of binding are dependent on specific phosphopeptides. Binding of the Shc PTB domain to tyrosine-phosphorylated peptides from TrkA, epidermal growth factor, ErbB3, and insulin receptors is achieved via an overall entropy-driven reaction. On the other hand, recognition of the phosphopeptides of insulin and interleukin-4 receptors by the IRS-1 PTB domain is predominantly an enthalpy-driven process. Mutagenesis and amino acid substitution experiments showed that in addition to the tyrosine-phosphorylated NPXY motif, the PTB domains of Shc and IRS-1 prefer a large hydrophobic residue at pY-5 and a small hydrophobic residue at pY-1, respectively (where pY is phosphotyrosine). These results agree with the calculated solvent accessibility of these two key peptide residues in the PTB domain/peptide structures and support the notion that the PTB domains of Shc and IRS-1 employ functionally distinct mechanisms to recognize tyrosine-phosphorylated receptors.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Changes in the NMR-derived motional parameters of the insulin receptor substrate 1 phosphotyrosine binding domain upon binding to an interleukin 4 receptor phosphopeptide.

Proteins recognize ligands by forming specific intermolecular interactions that often involve solvent exposed residues. Changes in the motional properties of these residues upon binding can affect the conformational entropy of the system and thus are related to the energetics of binding. The role that dynamics plays in ligand recognition can be investigated by comparing the motional properties of a free and ligated protein. NMR relaxation studies are well suited for examining changes in dynamics, especially for motions on a nanosecond to picosecond time scale. Recently, we determined the solution structure of the phosphotyrosine binding (PTB) domain of the insulin receptor substrate (IRS-1) complexed to a tyrosine-phosphorylated peptide derived from the interleukin 4 (IL-4) receptor [Zhou et al., (1996) Nat. Struct. Biol. 3, 388-393]. The peptide binds tightly to the protein in a surface exposed pocket, resulting in the partial burial of many protein residues. Using NMR relaxation studies, the dynamics of the backbone nitrogens of IRS-1 PTB domain were studied in both the free protein and the protein when complexed to the IL-4 receptor phosphopeptide. The backbone nitrogens of many residues that make important contacts to the ligand are motionally restricted in the free and complexed protein. Additional residues become motionally restricted only after ligand binding, including several residues that do not make any direct contacts with the ligand. These observed changes in the dynamics are compared to structural features of the complex.

Amino Acid Sequence↗
PubMed1997

Evidence for a requirement for both phospholipid and phosphotyrosine binding via the Shc phosphotyrosine-binding domain in vivo.

The adapter protein Shc is a critical component of mitogenic signaling pathways initiated by a number of receptors. Shc can directly bind to several tyrosine-phosphorylated receptors through its phosphotyrosine-binding (PTB) domain, and a role for the PTB domain in phosphotyrosine-mediated signaling has been well documented. The structure of the Shc PTB domain demonstrated a striking homology to the structures of pleckstrin homology domains, which suggested acidic phospholipids as a second ligand for the Shc PTB domain. Here we demonstrate that Shc binding via its PTB domain to acidic phospholipids is as critical as binding to phosphotyrosine for leading to Shc phosphorylation. Through structure-based, targeted mutagenesis of the Shc PTB domain, we first identified the residues within the PTB domain critical for phospholipid binding in vitro. In vivo, the PTB domain was essential for localization of Shc to the membrane, as mutant Shc proteins that failed to interact with phospholipids in vitro also failed to localize to the membrane. We also observed that PTB domain-dependent targeting to the membrane preceded the PTB domain's interaction with the tyrosine-phosphorylated receptor and that both events were essential for tyrosine phosphorylation of Shc following receptor activation. Thus, Shc, through its interaction with two different ligands, is able to accomplish both membrane localization and binding to the activated receptor via a single PTB domain.

Animals↗
PubMed1996

Structural basis for IL-4 receptor phosphopeptide recognition by the IRS-1 PTB domain.

We present the NMR structure of the PTB domain of insulin receptor substrate-1 (IRS-1) complexed to a tyrosine-phosphorylated peptide derived from the IL-4 receptor. Despite the lack of sequence homology and different binding specificity, the overall fold of the protein is similar to that of the Shc PTB domain and closely resembles that of PH domains. However, the PTB domain of IRS-1 is smaller than that of Shc (110 versus 170 residues) and binds to phosphopeptides in a distinct manner. We explain the phosphopeptide binding specificity based on the structure of the complex and results of site-directed mutagenesis experiments.

Amino Acid Sequence↗
PubMed1995

Binding affinities of tyrosine-phosphorylated peptides to the COOH-terminal SH2 and NH2-terminal phosphotyrosine binding domains of Shc.

The adaptor protein Shc has been implicated in Ras signaling via association with many tyrosine-phosphorylated receptors, including growth factor receptors, antigen receptors on T and B cells, and cytokine receptors. Shc could interact with the activated receptors through the carboxyl-terminal Src homology 2 (SH2) domain or the structurally unrelated amino-terminal phosphotyrosine binding (PTB) domain. Using NMR and surface plasmon resonance techniques, we have measured the binding affinities of the SH2 and the PTB domains of Shc to a series of phosphotyrosine-containing peptides derived from known Shc binding sites. Tyrosine-phosphorylated peptides derived from Trk (pY490), polyoma virus middle T-antigen (pY250), ErbB3 (pY1309), and epidermal growth factor receptor (pY1086, pY1148, and pY1114) that contain NPXpY sequences bind preferentially to the PTB domain of Shc with Kd values of 0.02-5.3 microM. The binding affinities of these peptides to the Shc SH2 domain were in the range of 220-1290 microM. In contrast, tyrosine-phosphorylated peptides from epidermal growth factor receptor (pY992, pY1173) and the zeta chain of the T-cell receptor bind preferentially to the SH2 domain (Kd = 50-130 microM) versus the PTB domain (Kd > 680 microM). From these studies, the relative contribution of the individual domains of Shc for binding to the phosphotyrosine-containing portions of these proteins was determined. In addition, our data indicate that the high affinity binding of the PTB domain to the NPXpY-containing peptides results from a very high association rate and a rapid dissociation rate, which is similar to previous results observed for the SH2-phosphopeptide complexes.

Amino Acid Sequence↗
PubMed1995

Structure and ligand recognition of the phosphotyrosine binding domain of Shc.

The nuclear magnetic resonance structure of the phosphotyrosine binding (PTB) domain of Shc complexed to a phosphopeptide reveals an alternative means of recognizing tyrosine-phosphorylated proteins. Unlike in SH2 domains, the phosphopeptide forms an antiparallel beta-strand with a beta-sheet of the protein, interacts with a hydrophobic pocket through the (pY-5) residue, and adopts a beta-turn. The PTB domain is structurally similar to pleckstrin homology domains (a beta-sandwich capped by an alpha-helix) and binds to acidic phospholipids, suggesting a possible role in membrane localization.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Solution structure of the Shc SH2 domain complexed with a tyrosine-phosphorylated peptide from the T-cell receptor.

She is a widely expressed adapter protein that plays an important role in signaling via a variety of cell surface receptors and has been implicated in coupling the stimulation of growth factor, cytokine, and antigen receptors to the Ras signaling pathway. She interacts with several tyrosine-phosphorylated receptors through its C-terminal SH2 domain, and one of the mechanisms of T-cell receptor-mediated Ras activation involves the interaction of the Shc SH2 domain with the tyrosine-phosphorylated zeta chain of the T-cell receptor. Here we describe a high-resolution NMR structure of the Shc SH2 domain complexed to a phosphopeptide (GHDGLpYQGLSTATK) corresponding to a portion of the zeta chain of the T-cell receptor. Although the overall architecture of the protein is similar to other SH2 domains, distinct structural differences were observed in the smaller beta-sheet, BG loop, (pY + 3) phosphopeptide-binding site, and relative position of the bound phosphopeptide.

Adaptor Proteins, Signal Transducing↗