Fibroin modulator‐binding protein 1 ( FMBP ‐1) is a silkworm transcription factor that has a unique DNA ‐binding domain called the one score and three amino acid peptide repeat ( STPR ). Here we used fluorescence correlation spectroscopy ( FCS ) to analyze the diffusion properties of an enhanced green fluorescent protein‐tagged FMBP ‐1 protein ( EGFP ‐ FMBP ‐1) expressed in posterior silk gland ( PSG ) cells of Bombyx mori at the same developmental stage as natural FMBP ‐1 expression. EGFP ‐ FMBP ‐1 clearly localized to cell nuclei. From the FCS analyses, we identified an immobile DNA ‐bound component and three discernible diffusion components. We also used FCS to observe the movements of wild‐type and mutant EGFP ‐ FMBP ‐1 proteins in HeLa cells, a simpler experimental system. Based on previous in vitro observation, we also introduced a single amino acid substitution in order to suppress stable FMBP ‐1‐ DNA binding; specifically, we replaced the ninth Arg in the third repeat within the STPR domain with Ala. This mutation completely disrupted the slowest diffusion component as well as the immobile component. The diffusion properties of other FMBP ‐1 mutants (e.g. mutants with N‐terminal or C‐terminal truncations) were also analyzed. Based on our observations, we suggest that the four identifiable movements might correspond to four distinct FMBP ‐1 states: (a) diffusion of free protein, (b) and (c) two types of transient interactions between FMBP ‐1 and chromosomal DNA , and (d) stable binding of FMBP ‐1 to chromosomal DNA .

The STPR motif is composed of 23-amino acid repeats aligned contiguously. STPR was originally reported as the DNA-binding domain of the silkworm protein FMBP-1. ZNF821, the human protein that contains the STPR domain, is a zinc finger protein of unknown function. In this study, we prepared peptides of silkworm FMBP-1 STPR (sSTPR) and human ZNF821 STPR (hSTPR) and compared their DNA binding behaviors. This revealed that hSTPR, like sSTPR, is a double-stranded DNA-binding domain. Sequence-independent DNA binding affinities and α-helix-rich DNA-bound structures were comparable between the two STPRs, although the specific DNA sequence of hSTPR is still unclear. In addition, a subcellular expression experiment showed that the hSTPR domain is responsible for the nuclear localization of ZNF821. ZNF821 showed a much slower diffusion rate in the nucleus, suggesting the possibility of interaction with chromosomal DNA. STPR sequences are found in many proteins from vertebrates, insects, and nematodes. Some of the consensus amino acid residues would be responsible for DNA binding and concomitant increases in α-helix structure content.

will examinL thLsL daLa m morL detai]s te absess thermodynarnic properties of dsoTdered regions m proteins 1P078

No abstract

the cell The mechansms ef targLt recogmtion of RBP have been gLudicd by exarnmmg high resolution thrcLdimcngional {3D) btructuie of RBPRNA complex The analyg]s of thLge 3D struLtures gave an mstght that RBPg use altphatiL tsurfdLe to ieLogmze RNA prefeTably One oi the RBPs YOVA uses guLh ai ahphatic burfaLe wnsistang of t"o glycines and onc alanmL toi bpeufiL recognition ot uracil The rep]aceinenL of urac]1 to bulkier puime nucleotide was suggested