protected function protocolHeader($method, $uri, CredentialsInterface $credentials, array $bodyParameters = array())
    {
        $parameters = array_merge(
            $this->baseProtocolParameters(),
            $this->additionalProtocolParameters(),
            array(
                'oauth_token' => $credentials->getIdentifier(),
            )
        );

        $this->signature->setCredentials($credentials);

        $parameters['oauth_signature'] = $this->signature->sign(
            $uri,
            array_merge($parameters, $bodyParameters),
            $method
        );

        return $this->normalizeProtocolParameters($parameters);
    }